[ { "id": "authors:e7ht6-p6826", "collection": "authors", "collection_id": "e7ht6-p6826", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210914-225403874", "type": "article", "title": "Euclid Preparation. XIV. The Complete Calibration of the Color\u2013Redshift Relation (C3R2) Survey: Data Release 3", "author": [ { "family_name": "Stanford", "given_name": "S. A.", "orcid": "0000-0003-0122-0841", "clpid": "Stanford-Specncer-A" }, { "family_name": "Masters", "given_name": "D.", "orcid": "0000-0001-5382-6138", "clpid": "Masters-Daniel-C" }, { "family_name": "Darvish", "given_name": "B.", "orcid": "0000-0003-4919-9017", "clpid": "Darvish-Behnam" }, { "family_name": "Stern", "given_name": "D.", "orcid": "0000-0003-2686-9241", "clpid": "Stern-Daniel" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Capak", "given_name": "P.", "orcid": "0000-0003-3578-6843", "clpid": "Capak-Peter" }, { "family_name": "Hernitschek", "given_name": "N.", "orcid": "0000-0003-1681-0430", "clpid": "Hernitschek-Nina" }, { "family_name": "Davidzon", "given_name": "I.", "orcid": "0000-0002-2951-7519" }, { "family_name": "Rhodes", "given_name": "J.", "orcid": "0000-0002-4485-8549", "clpid": "Rhodes-Jason-D" }, { "family_name": "Sanders", "given_name": "D. B.", "orcid": "0000-0002-1233-9998" }, { "family_name": "Mobasher", "given_name": "B." }, { "family_name": "Castander", "given_name": "F. J.", "orcid": "0000-0001-7316-4573" }, { "family_name": "Paltani", "given_name": "S.", "orcid": "0000-0002-8108-9179" }, { "family_name": "Aghanim", "given_name": "N.", "orcid": "0000-0002-6688-8992" }, { "family_name": "Amara", "given_name": "A." }, { "family_name": "Auricchio", "given_name": "N." }, { "family_name": "Balestra", "given_name": "A." }, { "family_name": "Bender", "given_name": "R.", "orcid": "0000-0001-7179-0626" }, { "family_name": "Bodendorf", "given_name": "C." }, { "family_name": "Bonino", "given_name": "D." }, { "family_name": "Branchini", "given_name": "E.", "orcid": "0000-0002-0808-6908" }, { "family_name": "Brinchmann", "given_name": "J.", "orcid": "0000-0003-4359-8797" }, { "family_name": "Capobianco", "given_name": "V." }, { "family_name": "Carbone", "given_name": "C." }, { "family_name": "Carretero", "given_name": "J.", "orcid": "0000-0002-3130-0204" }, { "family_name": "Casas", "given_name": "R." }, { "family_name": "Castellano", "given_name": "M.", "orcid": "0000-0001-9875-8263" }, { "family_name": "Cavuoti", "given_name": "S.", "orcid": "0000-0002-3787-4196" }, { "family_name": "Cimatti", "given_name": "A.", "orcid": "0000-0002-4409-5633" }, { "family_name": "Cledassou", "given_name": "R." }, { "family_name": "Conselice", "given_name": "C. J.", "orcid": "0000-0003-1949-7638" }, { "family_name": "Corcione", "given_name": "L." }, { "family_name": "Costille", "given_name": "A." }, { "family_name": "Cropper", "given_name": "M." }, { "family_name": "Degaudenzi", "given_name": "H." }, { "family_name": "Douspis", "given_name": "M." }, { "family_name": "Dubath", "given_name": "F." }, { "family_name": "Dusini", "given_name": "S." }, { "family_name": "Fosalba", "given_name": "P.", "orcid": "0000-0002-1510-5214" }, { "family_name": "Frailis", "given_name": "M." }, { "family_name": "Franceschi", "given_name": "E." }, { "family_name": "Franzetti", "given_name": "P." }, { "family_name": "Fumana", "given_name": "M." }, { "family_name": "Garilli", "given_name": "B.", "orcid": "0000-0001-7455-8750" }, { "family_name": "Giocoli", "given_name": "C." }, { "family_name": "Grupp", "given_name": "F." }, { "family_name": "Haugan", "given_name": "S. V. H." }, { "family_name": "Hoekstra", "given_name": "H.", "orcid": "0000-0002-0641-3231" }, { "family_name": "Holmes", "given_name": "W.", "clpid": "Holmes-Warren-A" }, { "family_name": "Hormuth", "given_name": "F." }, { "family_name": "Hudelot", "given_name": "P." }, { "family_name": "Jahnke", "given_name": "K.", "orcid": "0000-0003-3804-2137" }, { "family_name": "Kiessling", "given_name": "A." }, { "family_name": "Kilbinger", "given_name": "M.", "orcid": "0000-0001-9513-7138" }, { "family_name": "Kitching", "given_name": "T." }, { "family_name": "Kubik", "given_name": "B." }, { "family_name": "K\u00fcmmel", "given_name": "M." }, { "family_name": "Kunz", "given_name": "M.", "orcid": "0000-0003-1676-6126" }, { "family_name": "Kurki-Suonio", "given_name": "H." }, { "family_name": "Laureijs", "given_name": "R." }, { "family_name": "Ligori", "given_name": "S." }, { "family_name": "Lilje", "given_name": "P. B." }, { "family_name": "Lloro", "given_name": "I." }, { "family_name": "Maiorano", "given_name": "E." }, { "family_name": "Marggraf", "given_name": "O." }, { "family_name": "Markovic", "given_name": "K." }, { "family_name": "Massey", "given_name": "R.", "orcid": "0000-0002-6085-3780" }, { "family_name": "Meneghetti", "given_name": "M.", "orcid": "0000-0003-1225-7084", "clpid": "Meneghetti-Massimo" }, { "family_name": "Meylan", "given_name": "G." }, { "family_name": "Moscardini", "given_name": "L." }, { "family_name": "Niemi", "given_name": "S. M." }, { "family_name": "Padilla", "given_name": "C.", "orcid": "0000-0001-7951-0166" }, { "family_name": "Pasian", "given_name": "F." }, { "family_name": "Pedersen", "given_name": "K." }, { "family_name": "Pettorino", "given_name": "V.", "orcid": "0000-0002-4203-9320" }, { "family_name": "Pires", "given_name": "S." }, { "family_name": "Poncet", "given_name": "M." }, { "family_name": "Popa", "given_name": "L." }, { "family_name": "Pozzetti", "given_name": "L." }, { "family_name": "Raison", "given_name": "F." }, { "family_name": "Roncarelli", "given_name": "M.", "orcid": "0000-0001-9587-7822" }, { "family_name": "Rossetti", "given_name": "E." }, { "family_name": "Saglia", "given_name": "R.", "orcid": "0000-0003-0378-7032" }, { "family_name": "Scaramella", "given_name": "R." }, { "family_name": "Schneider", "given_name": "P.", "orcid": "0000-0002-5094-2245" }, { "family_name": "Secroun", "given_name": "A." }, { "family_name": "Seidel", "given_name": "G." }, { "family_name": "Serrano", "given_name": "S." }, { "family_name": "Sirignano", "given_name": "C." }, { "family_name": "Sirri", "given_name": "G." }, { "family_name": "Taylor", "given_name": "A. N." }, { "family_name": "Teplitz", "given_name": "H. I.", "orcid": "0000-0002-7064-5424", "clpid": "Teplitz-Harry-I" }, { "family_name": "Tereno", "given_name": "I." }, { "family_name": "Toledo-Moreo", "given_name": "R." }, { "family_name": "Valentijn", "given_name": "E. A." }, { "family_name": "Valenziano", "given_name": "L." }, { "family_name": "Verdoes Kleijn", "given_name": "G. A." }, { "family_name": "Wang", "given_name": "Y." }, { "family_name": "Zamorani", "given_name": "G.", "orcid": "0000-0002-2318-301X" }, { "family_name": "Zoubian", "given_name": "J." }, { "family_name": "Brescia", "given_name": "M.", "orcid": "0000-0001-9506-5680" }, { "family_name": "Congedo", "given_name": "G.", "orcid": "0000-0003-2508-0046" }, { "family_name": "Conversi", "given_name": "L." }, { "family_name": "Copin", "given_name": "Y.", "orcid": "0000-0002-5317-7518" }, { "family_name": "Kermiche", "given_name": "S." }, { "family_name": "Kohley", "given_name": "R." }, { "family_name": "Medinaceli", "given_name": "E." }, { "family_name": "Mei", "given_name": "S.", "orcid": "0000-0002-2849-559X" }, { "family_name": "Moresco", "given_name": "M.", "orcid": "0000-0002-7616-7136" }, { "family_name": "Morin", "given_name": "B." }, { "family_name": "Munari", "given_name": "E." }, { "family_name": "Polenta", "given_name": "G." }, { "family_name": "Sureau", "given_name": "F." }, { "family_name": "Tallada Cresp\u00ed", "given_name": "P." }, { "family_name": "Vassallo", "given_name": "T." }, { "family_name": "Zacchei", "given_name": "A." }, { "family_name": "Andreon", "given_name": "S." }, { "family_name": "Aussel", "given_name": "H.", "orcid": "0000-0002-1371-5705" }, { "family_name": "Baccigalupi", "given_name": "C." }, { "family_name": "Balaguera-Antol\u00ednez", "given_name": "A.", "orcid": "0000-0001-5028-3035" }, { "family_name": "Baldi", "given_name": "M.", "orcid": "0000-0003-4145-1943" }, { "family_name": "Bardelli", "given_name": "S.", "orcid": "0000-0002-8900-0298" }, { "family_name": "Biviano", "given_name": "A.", "orcid": "0000-0002-0857-0732" }, { "family_name": "Borsato", "given_name": "E." }, { "family_name": "Bozzo", "given_name": "E.", "orcid": "0000-0002-7504-7423" }, { "family_name": "Burigana", "given_name": "C." }, { "family_name": "Cabanac", "given_name": "R." }, { "family_name": "Camera", "given_name": "S.", "orcid": "0000-0003-3399-3574" }, { "family_name": "Cappi", "given_name": "A." }, { "family_name": "Carvalho", "given_name": "C. S." }, { "family_name": "Casas", "given_name": "S." }, { "family_name": "Castignani", "given_name": "G." }, { "family_name": "Colodro-Conde", "given_name": "C." }, { "family_name": "Coupon", "given_name": "J." }, { "family_name": "Courtois", "given_name": "H. M.", "orcid": "0000-0003-0509-1776" }, { "family_name": "Cuby", "given_name": "J.-G." }, { "family_name": "Da Silva", "given_name": "A." }, { "family_name": "de la Torre", "given_name": "S.", "orcid": "0000-0002-0839-2884" }, { "family_name": "Di Ferdinando", "given_name": "D." }, { "family_name": "Duncan", "given_name": "C. A. J." }, { "family_name": "Dupac", "given_name": "X." }, { "family_name": "Fabricius", "given_name": "M." }, { "family_name": "Farina", "given_name": "M." }, { "family_name": "Farrens", "given_name": "S." }, { "family_name": "Ferreira", "given_name": "P. G." }, { "family_name": "Finelli", "given_name": "F." }, { "family_name": "Flose-Reimberg", "given_name": "P." }, { "family_name": "Fotopoulou", "given_name": "S." }, { "family_name": "Galeotta", "given_name": "S." }, { "family_name": "Ganga", "given_name": "K." }, { "family_name": "Gillard", "given_name": "W." }, { "family_name": "Gozaliasl", "given_name": "G.", "orcid": "0000-0002-0236-919X" }, { "family_name": "Graci\u00e1-Carpio", "given_name": "J.", "orcid": "0000-0003-4689-3134" }, { "family_name": "Keihanen", "given_name": "E." }, { "family_name": "Kirkpatrick", "given_name": "C. C." }, { "family_name": "Lindholm", "given_name": "V." }, { "family_name": "Mainetti", "given_name": "G." }, { "family_name": "Maino", "given_name": "D.", "orcid": "0000-0002-4761-1242" }, { "family_name": "Martinet", "given_name": "N." }, { "family_name": "Marulli", "given_name": "F.", "orcid": "0000-0002-8850-0303" }, { "family_name": "Maturi", "given_name": "M." }, { "family_name": "Maurogordato", "given_name": "S." }, { "family_name": "Metcalf", "given_name": "R. B." }, { "family_name": "Nakajima", "given_name": "R." }, { "family_name": "Neissner", "given_name": "C." }, { "family_name": "Nightingale", "given_name": "J. W." }, { "family_name": "Nucita", "given_name": "A. A.", "orcid": "0000-0002-7926-3481" }, { "family_name": "Patrizii", "given_name": "L." }, { "family_name": "Potter", "given_name": "D." }, { "family_name": "Renzi", "given_name": "A.", "orcid": "0000-0001-9856-1970" }, { "family_name": "Riccio", "given_name": "G.", "orcid": "0000-0001-7020-1172" }, { "family_name": "Romelli", "given_name": "E." }, { "family_name": "S\u00e1nchez", "given_name": "A. G." }, { "family_name": "Sapone", "given_name": "D." }, { "family_name": "Schirmer", "given_name": "M.", "orcid": "0000-0003-2568-9994" }, { "family_name": "Schultheis", "given_name": "M.", "orcid": "0000-0002-6590-1657" }, { "family_name": "Scottez", "given_name": "V." }, { "family_name": "Stanco", "given_name": "L." }, { "family_name": "Tenti", "given_name": "M." }, { "family_name": "Teyssier", "given_name": "R.", "orcid": "0000-0001-7689-0933" }, { "family_name": "Torradeflot", "given_name": "F." }, { "family_name": "Valiviita", "given_name": "J." }, { "family_name": "Viel", "given_name": "M." }, { "family_name": "Whittaker", "given_name": "L." }, { "family_name": "Zucca", "given_name": "E.", "orcid": "0000-0002-5845-8132" } ], "abstract": "The Complete Calibration of the Color\u2013Redshift Relation (C3R2) survey is obtaining spectroscopic redshifts in order to map the relation between galaxy color and redshift to a depth of i \u223c 24.5 (AB). The primary goal is to enable sufficiently accurate photometric redshifts for Stage iv dark energy projects, particularly Euclid and the Nancy Grace Roman Space Telescope (Roman), which are designed to constrain cosmological parameters through weak lensing. We present 676 new high-confidence spectroscopic redshifts obtained by the C3R2 survey in the 2017B\u20132019B semesters using the DEIMOS, LRIS, and MOSFIRE multiobject spectrographs on the Keck telescopes. Combined with the 4454 redshifts previously published by this project, the C3R2 survey has now obtained and published 5130 high-quality galaxy spectra and redshifts. If we restrict consideration to only the 0.2 < z_p < 2.6 range of interest for the Euclid cosmological goals, then with the current data release, C3R2 has increased the spectroscopic redshift coverage of the Euclid color space from 51% (as reported by Masters et al.) to the current 91%. Once completed and combined with extensive data collected by other spectroscopic surveys, C3R2 should provide the spectroscopic calibration set needed to enable photometric redshifts to meet the cosmology requirements for Euclid, and make significant headway toward solving the problem for Roman.", "doi": "10.3847/1538-4365/ac0833", "issn": "0067-0049", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Supplement Series", "publication_date": "2021-09", "series_number": "1", "volume": "256", "issue": "1", "pages": "Art. No. 9" }, { "id": "authors:wvdg2-73f78", "collection": "authors", "collection_id": "wvdg2-73f78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190918-100141595", "type": "article", "title": "Uncle Jesse and the seven \"early career\" ladies of the night", "author": [ { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Kayser", "given_name": "Susan", "clpid": "Kayser-S" }, { "family_name": "Peterson", "given_name": "A. Victoria", "clpid": "Peterson-A-V" }, { "family_name": "Sargent", "given_name": "Anneila", "orcid": "0000-0002-4633-5098", "clpid": "Sargent-A-I" }, { "family_name": "Trimble", "given_name": "Virginia", "clpid": "Trimble-V-L" }, { "family_name": "Weistrop", "given_name": "Donna", "clpid": "Weistrop-D" } ], "abstract": "Jesse Leonard Greenstein (1909\u20132002) was apparently a very hard sell when it came to women in astronomy. Early in his autobiography, he wrote of \"Miss Payne, a person of wide culture and astronomical knowledge. The obvious discrimination against her as a woman scientist, worthy of normal academic recognition, exacerbated the stressful life she led. She was unhappy, emotional, in a rivalry with Menzel and Plaskett.\" She (a.k.a. Cecilia Helena Payne, later Gaposchkin) is the only woman with an explicit mention in that memoir, and Greenstein's impression of her left him uncertain whether women belonged in astronomy. In addition, some of us remember him as saying there was no use in educating women through to a Ph.D. because they only get married and quit.", "doi": "10.1119/1.5122880", "issn": "0002-9505", "publisher": "American Association of Physics Teachers", "publication": "American Journal of Physics", "publication_date": "2019-10", "series_number": "10", "volume": "87", "issue": "10", "pages": "778-783" }, { "id": "authors:t66na-6pq26", "collection": "authors", "collection_id": "t66na-6pq26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200824-122637398", "type": "article", "title": "Focal Ratio Degradation for Fiber Positioner Operation in Astronomical Spectrographs", "author": [ { "family_name": "Belland", "given_name": "Brent", "clpid": "Belland-B" }, { "family_name": "Gunn", "given_name": "James", "clpid": "Gunn-J-E" }, { "family_name": "Reiley", "given_name": "Dan", "clpid": "Reiley-D" }, { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Kirby", "given_name": "Evan", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "de Oliveira", "given_name": "Antonio Cesar", "clpid": "de-Oliveira-A-C" }, { "family_name": "de Oliveira", "given_name": "Ligia Souza", "orcid": "0000-0001-7670-0204", "clpid": "de-Oliveira-L-S" }, { "family_name": "Roberts", "given_name": "Mitsuko", "clpid": "Roberts-Mitsuko" }, { "family_name": "Seiffert", "given_name": "Michael", "clpid": "Seiffert-M" } ], "abstract": "Focal ratio degradation (FRD), the decrease of light's focal ratio between the input into an optical fiber and the output, is important to characterize for astronomical spectrographs due to its effects on throughput and the point spread function. However, while FRD is a function of many fiber properties such as stresses, microbending, and surface imperfections, angular misalignments between the incoming light and the face of the fiber also affect the light profile and complicate this measurement. A compact experimental setup and a model separating FRD from angular misalignment was applied to a fiber subjected to varying stresses or angular misalignments to determine the magnitude of these effects. The FRD was then determined for a fiber in a fiber positioner that will be used in the Subaru Prime Focus Spectrograph (PFS). The analysis we carried out for the PFS positioner suggests that effects of angular misalignment dominate and no significant FRD increase due to stress should occur.", "doi": "10.1142/s2251171719500077", "issn": "2251-1717", "publisher": "World Scientific Publishing", "publication": "Journal of Astronomical Instrumentation", "publication_date": "2019-09", "series_number": "3", "volume": "8", "issue": "3", "pages": "Art. No. 1950007" }, { "id": "authors:nqp29-5fg96", "collection": "authors", "collection_id": "nqp29-5fg96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190521-144030880", "type": "article", "title": "The Complete Calibration of the Color-Redshift Relation (C3R2) Survey: Analysis and Data Release 2", "author": [ { "family_name": "Masters", "given_name": "Daniel C.", "orcid": "0000-0001-5382-6138", "clpid": "Masters-D-C" }, { "family_name": "Stern", "given_name": "Daniel K.", "orcid": "0000-0003-2686-9241", "clpid": "Stern-D" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Capak", "given_name": "Peter L.", "orcid": "0000-0003-3578-6843", "clpid": "Capak-P" }, { "family_name": "Stanford", "given_name": "S. Adam", "clpid": "Stanford-S-A" }, { "family_name": "Hernitschek", "given_name": "Nina", "orcid": "0000-0003-1681-0430", "clpid": "Hernitschek-N" }, { "family_name": "Galametz", "given_name": "Audrey", "orcid": "0000-0002-1504-8117", "clpid": "Galametz-A" }, { "family_name": "Davidzon", "given_name": "Iary", "orcid": "0000-0002-2951-7519", "clpid": "Davidzon-I" }, { "family_name": "Rhodes", "given_name": "Jason D.", "orcid": "0000-0002-4485-8549", "clpid": "Rhodes-J-D" }, { "family_name": "Sanders", "given_name": "Dave", "orcid": "0000-0002-1233-9998", "clpid": "Sanders-D-B" }, { "family_name": "Mobasher", "given_name": "Bahram", "clpid": "Mobasher-B" }, { "family_name": "Castander", "given_name": "Francisco", "orcid": "0000-0001-7316-4573", "clpid": "Castander-F-J" }, { "family_name": "Pruett", "given_name": "Kerianne", "clpid": "Pruett-K" }, { "family_name": "Fotopoulou", "given_name": "Sotiria", "orcid": "0000-0002-9686-254X", "clpid": "Fotopoulou-S" } ], "abstract": "The Complete Calibration of the Color-Redshift Relation (C3R2) survey is a multi-institution, multi-instrument survey that aims to map the empirical relation of galaxy color to redshift to i ~ 24.5 (AB), thereby providing a firm foundation for weak lensing cosmology with the Stage IV dark energy missions Euclid and WFIRST. Here we present 3171 new spectroscopic redshifts obtained in the 2016B and 2017A semesters with a combination of DEIMOS, LRIS, and MOSFIRE on the Keck telescopes. The observations come from all of the Keck partners: Caltech, NASA, the University of Hawaii, and the University of California. Combined with the 1283 redshifts published in DR1, the C3R2 survey has now obtained and published 4454 high-quality galaxy redshifts. We discuss updates to the survey design and provide a catalog of photometric and spectroscopic data. Initial tests of the calibration method performance are given, indicating that the sample, once completed and combined with extensive data collected by other spectroscopic surveys, should allow us to meet the cosmology requirements for Euclid, and make significant headway toward solving the problem for WFIRST. We use the full spectroscopic sample to demonstrate that galaxy brightness is weakly correlated with redshift once a galaxy is localized in the Euclid or WFIRST color space, with potentially important implications for the spectroscopy needed to calibrate redshifts for faint WFIRST and LSST sources.", "doi": "10.3847/1538-4357/ab184d", "issn": "1538-4357", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2019-06-01", "series_number": "2", "volume": "877", "issue": "2", "pages": "Art. No. 81" }, { "id": "authors:9fp8h-28c46", "collection": "authors", "collection_id": "9fp8h-28c46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190123-090243442", "type": "article", "title": "Precision Distances to Dwarf Galaxies and Globular Clusters from Pan-STARRS1 3\u03c0 RR Lyrae", "author": [ { "family_name": "Hernitschek", "given_name": "Nina", "orcid": "0000-0003-1681-0430", "clpid": "Hernitschek-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Rix", "given_name": "Hans-Walter", "orcid": "0000-0003-4996-9069", "clpid": "Rix-H-W" }, { "family_name": "Magnier", "given_name": "Eugene", "orcid": "0000-0002-7965-2815", "clpid": "Magnier-E-A" }, { "family_name": "Metcalfe", "given_name": "Nigel", "orcid": "0000-0001-9034-4402", "clpid": "Metcalfe-N" }, { "family_name": "Wainscoat", "given_name": "Richard", "orcid": "0000-0002-1341-0952", "clpid": "Wainscoat-R-J" }, { "family_name": "Waters", "given_name": "Christopher", "clpid": "Waters-C-W" }, { "family_name": "Kudritzki", "given_name": "Rolf-Peter", "clpid": "Kudritzki-R-P" }, { "family_name": "Burgett", "given_name": "William", "orcid": "0000-0003-4401-9582", "clpid": "Burgett-W" } ], "abstract": "We present new spatial models and distance estimates for globular clusters and dwarf spheroidals orbiting our Galaxy based on RR Lyrae (RRab) stars in the Pan-STARRS1 (PS1) 3\u03c0 survey. Using the PS1 sample of RRab stars from Sesar et al. in 16 globular clusters and 5 dwarf galaxies, we fit structural models in (l, b, D) space; for 13 globular clusters and 6 dwarf galaxies, we give only their mean heliocentric distance D. We verify the accuracy of the period\u2013luminosity relations used in Sesar et al. to constrain the distance to those stars, and compare them to period\u2013luminosity\u2013metallicity relations using metallicities from Carretta et al. We compare our Sesar et al. distances to the parallax-based Gaia DR2 distance estimates from Bailer-Jones et al. and find our distances to be consistent and considerably more precise.", "doi": "10.3847/1538-4357/aaf388", "issn": "1538-4357", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2019-01-20", "series_number": "1", "volume": "871", "issue": "1", "pages": "Art. No. 49" }, { "id": "authors:jpggk-c7a97", "collection": "authors", "collection_id": "jpggk-c7a97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181130-091853410", "type": "article", "title": "SMHASH: a new mid-infrared RR Lyrae distance determination for the Local Group dwarf spheroidal galaxy Sculptor", "author": [ { "family_name": "Garofalo", "given_name": "Alessia", "clpid": "Garofalo-A" }, { "family_name": "Scowcroft", "given_name": "Victoria", "orcid": "0000-0001-8829-4653", "clpid": "Scowcroft-V" }, { "family_name": "Clementini", "given_name": "Gisella", "clpid": "Clementini-G" }, { "family_name": "Johnston", "given_name": "Kathryn V.", "orcid": "0000-0001-6244-6727", "clpid": "Johnston-K-V" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Freedman", "given_name": "Wendy L.", "orcid": "0000-0003-3431-9135", "clpid": "Freedman-W-L" }, { "family_name": "Madore", "given_name": "Barry F.", "orcid": "0000-0002-1576-1676", "clpid": "Madore-B-F" }, { "family_name": "Majewski", "given_name": "Steven R.", "orcid": "0000-0003-2025-3147", "clpid": "Majewski-S-R" }, { "family_name": "Monson", "given_name": "Andrew J.", "orcid": "0000-0002-0048-2586", "clpid": "Monson-A-J" }, { "family_name": "Neeley", "given_name": "Jillian R.", "clpid": "Neeley-J-R" }, { "family_name": "Grillmair", "given_name": "Carl J.", "orcid": "0000-0003-4072-169X", "clpid": "Grillmair-C-J" }, { "family_name": "Hendel", "given_name": "David", "orcid": "0000-0002-7939-7607", "clpid": "Hendel-D" }, { "family_name": "Kallivayalil", "given_name": "Nitya", "clpid": "Kallivayalil-N-J" }, { "family_name": "Marengo", "given_name": "Massimo", "orcid": "0000-0001-9910-9230", "clpid": "Marengo-M" }, { "family_name": "van der Marel", "given_name": "Roeland", "orcid": "0000-0001-7827-7825", "clpid": "van-der-Marel-R-P" } ], "abstract": "We present a new distance estimation for the Milky Way dwarf spheroidal satellite Sculptor obtained from multi-epoch mid-infrared observations of RR Lyrae stars (RRLs). The 3.6 \u03bcm observations have been acquired with the Infrared Array Camera onboard the Spitzer Space Telescope as part of the SMHASH program. Mid-infrared light curves for 42 RRLs were obtained, from which we measured Sculptor's distance modulus to be \u03bc = 19.60 \u00b1 0.02 (statistical) \u00b1 0.04 (photometric) mag (with \u03c3_(sys) = 0.09 mag), using the 3.6 \u03bcm empirical period\u2013luminosity relations derived from the Galactic globular cluster M4, or \u03bc = 19.57 \u00b1 0.02 (statistical) \u00b1 0.04 (photometric) mag (with \u03c3_(sys) = 0.11 mag) using empirical relations in the same passband recently derived from the Large Magellanic Cloud globular cluster Reticulum. Both these measurements are in good agreement with values presented in previous works with Sculptor RRLs in optical bands, and are also consistent with recent near-infrared RR Lyrae results. Best agreement with the literature is found for the latter modulus which is equivalent to a distance of d = 82 \u00b1 1 (statistical) \u00b1 2 (photometric) kpc (with \u03c3_(sys) = 4 kpc). Finally, using a subsample of RRLs with spectroscopic metallicities, we demonstrate that these distance estimates are not affected by metallicity effects.", "doi": "10.1093/mnras/sty2222", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2018-11-21", "series_number": "1", "volume": "481", "issue": "1", "pages": "578-595" }, { "id": "authors:bs5rf-dbn19", "collection": "authors", "collection_id": "bs5rf-dbn19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180830-082915316", "type": "article", "title": "SMHASH: anatomy of the Orphan Stream using RR Lyrae stars", "author": [ { "family_name": "Hendel", "given_name": "David", "orcid": "0000-0002-7939-7607", "clpid": "Hendel-D" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Grillmair", "given_name": "Carl J.", "orcid": "0000-0003-4072-169X", "clpid": "Grillmair-C-J" } ], "abstract": "Stellar tidal streams provide an opportunity to study the motion and structure of the disrupting galaxy as well as the gravitational potential of its host. Streams around the Milky Way are especially promising as phase space positions of individual stars will be measured by ongoing or upcoming surveys. Nevertheless, it remains a challenge to accurately assess distances to stars farther than 10 kpc from the Sun, where we have the poorest knowledge of the Galaxy's mass distribution. To address this, we present observations of 32 candidate RR Lyrae stars in the Orphan tidal stream taken as part of the Spitzer Merger History and Shape of the Galactic Halo (SMHASH) program. The extremely tight correlation between the periods, luminosities, and metallicities of RR Lyrae variable stars in the Spitzer IRAC 3.6\u03bcm band allows the determination of precise distances to individual stars; the median statistical relative distance uncertainty to each RR Lyrae star is 2.5\u2009per\u2009cent. By fitting orbits in an example potential, we obtain an upper limit on the mass of the Milky Way interior to 60 kpc of 5.6^(+1.2)_(\u22121.1)\u00d710^(11) M\u2299, bringing estimates based on the Orphan Stream in line with those using other tracers. The SMHASH data also resolve the stream in line-of-sight depth, allowing a new perspective on the internal structure of the disrupted dwarf galaxy. Comparing with N\u2013body models, we find that the progenitor had an initial dark halo mass of approximately 3.2 \u00d7 109\u2009M\u2299, placing the Orphan Stream's progenitor amongst the classical dwarf spheroidals.", "doi": "10.1093/mnras/sty1455", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2018-09-01", "series_number": "1", "volume": "479", "issue": "1", "pages": "570-587" }, { "id": "authors:xdcnw-40p66", "collection": "authors", "collection_id": "xdcnw-40p66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190107-144131759", "type": "book_section", "title": "Prime Focus Spectrograph (PFS) for the Subaru telescope: ongoing integration and future plans", "book_title": "Ground-based and Airborne Instrumentation for Astronomy VII", "author": [ { "family_name": "Tamura", "given_name": "Naoyuki", "clpid": "Tamura-Naoyuki" }, { "family_name": "Burnham", "given_name": "Jill A.", "clpid": "Burnham-J-A" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Dekany", "given_name": "Richard G.", "clpid": "Dekany-Richard" }, { "family_name": "Hover", "given_name": "David J.", "clpid": "Hover-D-J" }, { "family_name": "Reiley", "given_name": "Daniel J.", "clpid": "Reiley-D-J" }, { "family_name": "Roberts", "given_name": "Mitsuko", "clpid": "Roberts-Mitsuko" } ], "contributor": [ { "family_name": "Evans", "given_name": "Christopher J.", "clpid": "Evans-C-J" }, { "family_name": "Simard", "given_name": "Luc", "clpid": "Simard-L" }, { "family_name": "Takami", "given_name": "Hideki", "clpid": "Takami-Hideki" } ], "abstract": "PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ~ 1.6-2.7\u00c5. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project recently started undertaking the commissioning process of a subsystem at the Subaru Telescope side, with the integration and test processes of the other subsystems ongoing in parallel. We are aiming to start engineering night-sky operations in 2019, and observations for scientific use in 2021. This article gives an overview of the instrument, current project status and future paths forward.", "doi": "10.1117/12.2311871", "isbn": "9781510619579", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "2018-07-27", "pages": "Art. No. 107021C" }, { "id": "authors:enav7-t3335", "collection": "authors", "collection_id": "enav7-t3335", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180522-102929095", "type": "article", "title": "The Profile of the Galactic Halo from Pan-STARRS1 3\u03c0 RR Lyrae", "author": [ { "family_name": "Hernitschek", "given_name": "Nina", "orcid": "0000-0003-1681-0430", "clpid": "Hernitschek-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Rix", "given_name": "Hans-Walter", "orcid": "0000-0003-4996-9069", "clpid": "Rix-H-W" }, { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Martin", "given_name": "Nicolas F.", "orcid": "0000-0002-1349-202X", "clpid": "Martin-N-F" }, { "family_name": "Magnier", "given_name": "Eugene", "orcid": "0000-0002-7965-2815", "clpid": "Magnier-E-A" }, { "family_name": "Wainscoat", "given_name": "Richard", "orcid": "0000-0002-1341-0952", "clpid": "Wainscoat-R-J" }, { "family_name": "Kaiser", "given_name": "Nick", "orcid": "0000-0001-6511-4306", "clpid": "Kaiser-N" }, { "family_name": "Tonry", "given_name": "John L.", "orcid": "0000-0003-2858-9657", "clpid": "Tonry-J-L" }, { "family_name": "Kudritzki", "given_name": "Rolf-Peter", "clpid": "Kudritzki-R-P" }, { "family_name": "Hodapp", "given_name": "Klaus", "orcid": "0000-0003-0786-2140", "clpid": "Hodapp-K-W" }, { "family_name": "Chambers", "given_name": "Ken", "orcid": "0000-0001-6965-7789", "clpid": "Chambers-K-C" }, { "family_name": "Flewelling", "given_name": "Heather", "orcid": "0000-0002-1050-4056", "clpid": "Flewelling-H" }, { "family_name": "Burgett", "given_name": "William", "orcid": "0000-0003-4401-9582", "clpid": "Burgett-W" } ], "abstract": "We characterize the spatial density of the Pan-STARRS1 (PS1) sample of Rrab stars to study the properties of the old Galactic stellar halo. This sample, containing 44,403 sources, spans galactocentric radii of 0.55 kpc \u2264 R_(gc) \u2264 141 kpc with a distance precision of 3% and thus is able to trace the halo out to larger distances than most previous studies. After excising stars that are attributed to dense regions such as stellar streams, the Galactic disk and bulge, and halo globular clusters, the sample contains ~11,000 sources within 20 kpc \u2264 R-(gc) \u2264 131 kpc. We then apply forward modeling using Galactic halo profile models with a sample selection function. Specifically, we use ellipsoidal stellar density models \u03c1(l, b, R gc) with a constant and a radius-dependent halo flattening q(R gc). Assuming constant flattening q, the distribution of the sources is reasonably well fit by a single power law with n = 4.40^(+0.05)_(-0.04) and q = 0.918^(+0.016)_(-0.014) and comparably well fit by an Einasto profile with n = 9.53^(+0.27)_(_-0.28), an effective radius r_(eff) = 1.07 \u00b1 0.10 kpc, and a halo flattening of q = 0.923 \u00b1 0.007. If we allow for a radius-dependent flattening q(R_(gc)), we find evidence for a distinct flattening of q ~ 0.8 of the inner halo at ~25 kpc. Additionally, we find that the south Galactic hemisphere is more flattened than the north Galactic hemisphere. The results of our work are largely consistent with many earlier results (e.g., Watkins et al.; Iorio et al.). We find that the stellar halo, as traced in RR Lyrae stars, exhibits a substantial number of further significant over- and underdensities, even after masking all known overdensities.", "doi": "10.3847/1538-4357/aabfbb", "issn": "1538-4357", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2018-05-20", "series_number": "1", "volume": "859", "issue": "1", "pages": "Art. No. 31" }, { "id": "authors:mj0km-2sg46", "collection": "authors", "collection_id": "mj0km-2sg46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180426-144524292", "type": "article", "title": "A Formation Timescale of the Galactic Halo from Mg Isotopes in Dwarf Stars", "author": [ { "family_name": "Carlos", "given_name": "Mar\u00edlia", "orcid": "0000-0003-1757-6666", "clpid": "Carlos-M" }, { "family_name": "Karakas", "given_name": "Amanda I.", "orcid": "0000-0002-3625-6951", "clpid": "Karakas-A-I" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Kobayashi", "given_name": "Chiaki", "orcid": "0000-0002-4343-0487", "clpid": "Kobayashi-Chiaki" }, { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" } ], "abstract": "We determine magnesium isotopic abundances of metal-poor dwarf stars from the galactic halo, to shed light on the onset of asymptotic giant branch (AGB) star nucleosynthesis in the galactic halo and constrain the timescale of its formation. We observed a sample of eight new halo K dwarfs in a metallicity range of \u22121.9 < [Fe/H] < \u22120.9 and 4200 < T_(eff)(K) < 4950, using the HIRES spectrograph at the Keck Observatory (R \u2248 10^5 and 200 \u2264 S/N \u2264 300). We obtain magnesium isotopic abundances by spectral synthesis on three MgH features and compare our results with galactic chemical evolution models. With the current sample, we almost double the number of metal-poor stars with Mg isotopes determined from the literature. The new data allow us to determine the metallicity when the ^(26)Mg abundances start to become important, [Fe/H] ~ \u22121.4 \u00b1 0.1. The data with [Fe/H] > \u22121.4 are somewhat higher (1\u20133\u03c3) than previous chemical evolution model predictions, indicating perhaps higher yields of the neutron-rich isotopes. Our results using only AGB star enrichment suggest a timescale for formation for the galactic halo of about 0.3 Gyr, but considering also supernova enrichment, the upper limit for the timescale formation is about 1.5 Gyr.", "doi": "10.3847/1538-4357/aab36c", "issn": "1538-4357", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2018-04-01", "series_number": "2", "volume": "856", "issue": "2", "pages": "Art. No. 161" }, { "id": "authors:je95b-9dz72", "collection": "authors", "collection_id": "je95b-9dz72", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180226-135907227", "type": "article", "title": "Two chemically similar stellar overdensities on opposite sides of the plane of the Galactic disk", "author": [ { "family_name": "Bergemann", "given_name": "Maria", "orcid": "0000-0002-9908-5571", "clpid": "Bergemann-M" }, { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Serenelli", "given_name": "Aldo M.", "orcid": "0000-0001-6359-2769", "clpid": "Serenelli-A-M" }, { "family_name": "Sheffield", "given_name": "Allyson", "orcid": "0000-0003-2178-8792", "clpid": "Sheffield-A-A" }, { "family_name": "Li", "given_name": "Ting S.", "clpid": "Li-Ting-S" }, { "family_name": "Casagrande", "given_name": "Luca", "orcid": "0000-0003-2688-7511", "clpid": "Casagrande-L" }, { "family_name": "Johnston", "given_name": "Kathryn V.", "orcid": "0000-0001-6244-6727", "clpid": "Johnston-K-V" }, { "family_name": "Laporte", "given_name": "Chervin F. P.", "orcid": "0000-0003-3922-7336", "clpid": "Laporte-C-F-P" }, { "family_name": "Price-Whelan", "given_name": "Adrian M.", "orcid": "0000-0003-0872-7098", "clpid": "Price-Whelan-A" }, { "family_name": "Sch\u00f6nrich", "given_name": "Ralph", "clpid": "Sch\u00f6nrich-R" }, { "family_name": "Gould", "given_name": "Andrew", "clpid": "Gould-A-P" } ], "abstract": "Our Galaxy is thought to have an active evolutionary history, dominated over the past ten billion years or so by star formation, the accretion of cold gas and, in particular, the merging of clumps of baryonic and dark matter. The stellar halo\u2014the faint, roughly spherical component of the Galaxy\u2014reveals rich 'fossil' evidence of these interactions, in the form of stellar streams, substructures and chemically distinct stellar components. The effects of interactions with dwarf galaxies on the content and morphology of the Galactic disk are still being explored. Recent studies have identified kinematically distinct stellar substructures and moving groups of stars in our Galaxy, which may have extragalactic origins. There is also mounting evidence that stellar overdensities (regions with greater-than-average stellar density) at the interface between the outer disk and the halo could have been caused by the interaction of a dwarf galaxy with the disk. Here we report a spectroscopic analysis of 14 stars from two stellar overdensities, each lying about five kiloparsecs above or below the Galactic plane\u2014locations suggestive of an association with the stellar halo. We find that the chemical compositions of these two groups of stars are almost identical, both within and between these overdensities, and closely match the abundance patterns of stars in the Galactic disk. We conclude that these stars came from the disk, and that the overdensities that they are part of were created by tidal interactions of the disk with passing or merging dwarf galaxies.", "doi": "10.1038/nature25490", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2018-03-15", "series_number": "7696", "volume": "555", "issue": "7696", "pages": "334-337" }, { "id": "authors:wnmac-2bk34", "collection": "authors", "collection_id": "wnmac-2bk34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171113-103138961", "type": "article", "title": "The Outer Halo of the Milky Way as Probed by RR Lyr Variables from the Palomar Transient Facility", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Bahnolzer", "given_name": "Sophianna", "clpid": "Bahnolzer-S" }, { "family_name": "He", "given_name": "Kevin", "orcid": "0000-0001-5806-0370", "clpid": "He-Kevin" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Prince", "given_name": "Thomas A.", "orcid": "0000-0002-8850-3627", "clpid": "Prince-T-A" }, { "family_name": "Bellm", "given_name": "Eric", "orcid": "0000-0001-8018-5348", "clpid": "Bellm-E-C" }, { "family_name": "Laher", "given_name": "Russ R.", "orcid": "0000-0003-2451-5482", "clpid": "Laher-R-R" } ], "abstract": "RR Lyrae stars are ideal massless tracers that can be used to study the total mass and dark matter content of the outer halo of the Milky Way (MW). This is because they are easy to find in the light-curve databases of large stellar surveys and their distances can be determined with only knowledge of the light curve. We present here a sample of 112 RR Lyr stars beyond 50 kpc in the outer halo of the MW, excluding the Sgr streams, for which we have obtained moderate-resolution spectra with Deimos on the Keck II Telescope. Four of these have distances exceeding 100 kpc. These were selected from a much larger set of 447 candidate RR Lyr stars that were data-mined using machine-learning techniques applied to the light curves of variable stars in the Palomar Transient Facility database. The observed radial velocities taken at the phase of the variable corresponding to the time of observation were converted to systemic radial velocities in the Galactic standard of rest. From our sample of 112 RR Lyr stars we determine the radial velocity dispersion in the outer halo of the MW to be ~90 km s^(\u22121) at 50 kpc, falling to about 65 km s^(\u22121) near 100 kpc once a small number of major outliers are removed. With reasonable estimates of the completeness of our sample of 447 candidates and assuming a spherical halo, we find that the stellar density in the outer halo declines as r^(-4).", "doi": "10.3847/1538-4357/aa9120", "issn": "1538-4357", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2017-11-10", "series_number": "2", "volume": "849", "issue": "2", "pages": "Art. No. 150" }, { "id": "authors:qh6z4-zsz83", "collection": "authors", "collection_id": "qh6z4-zsz83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170525-151351304", "type": "article", "title": "The Complete Calibration of the Color-Redshift Relation (C3R2) Survey: Survey Overview and Data Release 1", "author": [ { "family_name": "Masters", "given_name": "Daniel C.", "orcid": "0000-0001-5382-6138", "clpid": "Masters-D-C" }, { "family_name": "Stern", "given_name": "Daniel K.", "orcid": "0000-0003-2686-9241", "clpid": "Stern-D" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Capak", "given_name": "Peter L.", "orcid": "0000-0003-3578-6843", "clpid": "Capak-P" }, { "family_name": "Rhodes", "given_name": "Jason D.", "orcid": "0000-0002-4485-8549", "clpid": "Rhodes-J-D" }, { "family_name": "Castander", "given_name": "Francisco J.", "orcid": "0000-0001-7316-4573", "clpid": "Castander-F-J" }, { "family_name": "Paltani", "given_name": "St\u00e9phane", "clpid": "Paltani-St\u00e9phane" } ], "abstract": "A key goal of the Stage IV dark energy experiments Euclid, LSST, and WFIRST is to measure the growth of structure with cosmic time from weak lensing analysis over large regions of the sky. Weak lensing cosmology will be challenging: in addition to highly accurate galaxy shape measurements, statistically robust and accurate photometric redshift (photo-z) estimates for billions of faint galaxies will be needed in order to reconstruct the three-dimensional matter distribution. Here we present an overview of and initial results from the Complete Calibration of the Color\u2013Redshift Relation (C3R2) survey, which is designed specifically to calibrate the empirical galaxy color\u2013redshift relation to the Euclid depth. These redshifts will also be important for the calibrations of LSST and WFIRST. The C3R2 survey is obtaining multiplexed observations with Keck (DEIMOS, LRIS, and MOSFIRE), the Gran Telescopio Canarias (GTC; OSIRIS), and the Very Large Telescope (VLT; FORS2 and KMOS) of a targeted sample of galaxies that are most important for the redshift calibration. We focus spectroscopic efforts on undersampled regions of galaxy color space identified in previous work in order to minimize the number of spectroscopic redshifts needed to map the color\u2013redshift relation to the required accuracy. We present the C3R2 survey strategy and initial results, including the 1283 high-confidence redshifts obtained in the 2016A semester and released as Data Release 1.", "doi": "10.3847/1538-4357/aa6f08", "issn": "1538-4357", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2017-06-01", "series_number": "2", "volume": "841", "issue": "2", "pages": "Art. No. 111" }, { "id": "authors:gkyk0-32912", "collection": "authors", "collection_id": "gkyk0-32912", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170410-132108269", "type": "article", "title": "Machine-learned Identification of RR Lyrae Stars from Sparse, Multi-band Data: The PS1 Sample", "author": [ { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Hernitschek", "given_name": "Nina", "orcid": "0000-0003-1681-0430", "clpid": "Hernitschek-N" }, { "family_name": "Mitrovi\u0107", "given_name": "Sandra", "clpid": "Mitrovi\u0107-S" }, { "family_name": "Ivezi\u0107", "given_name": "\u017deljko", "orcid": "0000-0001-5250-2633", "clpid": "Ivezi\u0107-\u017d" }, { "family_name": "Rix", "given_name": "Hans-Walter", "orcid": "0000-0003-4996-9069", "clpid": "Rix-H-W" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Bernard", "given_name": "Edouard J.", "clpid": "Bernard-E-J" }, { "family_name": "Grebel", "given_name": "Eva K.", "orcid": "0000-0002-1891-3794", "clpid": "Grebel-E-K" }, { "family_name": "Martin", "given_name": "Nicolas F.", "orcid": "0000-0002-1349-202X", "clpid": "Martin-N-F" }, { "family_name": "Schlafly", "given_name": "Edward F.", "orcid": "0000-0002-3569-7421", "clpid": "Schlafly-E-F" }, { "family_name": "Burgett", "given_name": "William S.", "clpid": "Burgett-W-S" }, { "family_name": "Draper", "given_name": "Peter W.", "orcid": "0000-0002-7204-9802", "clpid": "Draper-P-W" }, { "family_name": "Flewelling", "given_name": "Heather", "orcid": "0000-0002-1050-4056", "clpid": "Flewelling-H" }, { "family_name": "Kaiser", "given_name": "Nick", "orcid": "0000-0001-6511-4306", "clpid": "Kaiser-N" }, { "family_name": "Kudritzki", "given_name": "Rolf P.", "clpid": "Kudritzki-R-P" }, { "family_name": "Magnier", "given_name": "Eugene A.", "orcid": "0000-0002-7965-2815", "clpid": "Magnier-E-A" }, { "family_name": "Metcalfe", "given_name": "Nigel", "orcid": "0000-0001-9034-4402", "clpid": "Metcalfe-N" }, { "family_name": "Tonry", "given_name": "John L.", "orcid": "0000-0003-2858-9657", "clpid": "Tonry-J-L" }, { "family_name": "Waters", "given_name": "Christopher", "clpid": "Waters-C-W" } ], "abstract": "RR Lyrae stars may be the best practical tracers of Galactic halo (sub-)structure and kinematics. The PanSTARRS1 (PS1) 3\u03c0 survey offers multi-band, multi-epoch, precise photometry across much of the sky, but a robust identification of RR Lyrae stars in this data set poses a challenge, given PS1's sparse, asynchronous multi-band light curves (\u227e12 epochs in each of five bands, taken over a 4.5 year period). We present a novel template fitting technique that uses well-defined and physically motivated multi-band light curves of RR Lyrae stars, and demonstrate that we get accurate period estimates, precise to 2 s in >80% of cases. We augment these light-curve fits with other features from photometric time-series and provide them to progressively more detailed machine-learned classification models. From these models, we are able to select the widest (three-fourths of the sky) and deepest (reaching 120 kpc) sample of RR Lyrae stars to date. The PS1 sample of ~45,000 RRab stars is pure (90%) and complete (80% at 80 kpc) at high galactic latitudes. It also provides distances that are precise to 3%, measured with newly derived period\u2013luminosity relations for optical/near-infrared PS1 bands. With the addition of proper motions from Gaia and radial velocity measurements from multi-object spectroscopic surveys, we expect the PS1 sample of RR Lyrae stars to become the premier source for studying the structure, kinematics, and the gravitational potential of the Galactic halo. The techniques presented in this study should translate well to other sparse, multi-band data sets, such as those produced by the Dark Energy Survey and the upcoming Large Synoptic Survey Telescope Galactic plane sub-survey.", "doi": "10.3847/1538-3881/aa661b", "issn": "1538-3881", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2017-05", "series_number": "5", "volume": "153", "issue": "5", "pages": "Art. No. 204" }, { "id": "authors:506jv-naj24", "collection": "authors", "collection_id": "506jv-naj24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170329-095524041", "type": "article", "title": "Triangulum II. Not Especially Dense After All", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Simon", "given_name": "Joshua D.", "clpid": "Simon-J-D" }, { "family_name": "Guhathakurta", "given_name": "Puragra", "orcid": "0000-0001-8867-4234", "clpid": "Guhathakurta-P" }, { "family_name": "Thygesen", "given_name": "Anders O.", "orcid": "0000-0002-4912-1183", "clpid": "Thygesen-A-O" }, { "family_name": "Duggan", "given_name": "Gina E.", "orcid": "0000-0002-9256-6735", "clpid": "Duggan-G-E" } ], "abstract": "Among the Milky Way satellites discovered in the past three years, Triangulum II has presented the most difficulty in revealing its dynamical status. Kirby et al. identified it as the most dark-matter-dominated galaxy known, with a mass-to-light ratio within the half-light radius of 3600_(-2100)^(+3500)M_\u2609L_\u2609^(-1). On the other hand, Martin et al. measured an outer velocity dispersion that is 3.5 \u00b1 2.1 times larger than the central velocity dispersion, suggesting that the system might not be in equilibrium. From new multi-epoch Keck/DEIMOS measurements of 13 member stars in Triangulum II, we constrain the velocity dispersion to be \u03c3_v < 3.4 km s^(\u22121) (90% C.L.). Our previous measurement of \u03c3_v, based on six stars, was inflated by the presence of a binary star with variable radial velocity. We find no evidence that the velocity dispersion increases with radius. The stars display a wide range of metallicities, indicating that Triangulum II retained supernova ejecta and therefore possesses, or once possessed, a massive dark matter halo. However, the detection of a metallicity dispersion hinges on the membership of the two most metal-rich stars. The stellar mass is lower than galaxies of similar mean stellar metallicity, which might indicate that Triangulum II is either a star cluster or a tidally stripped dwarf galaxy. Detailed abundances of one star show heavily depressed neutron-capture abundances, similar to stars in most other ultra-faint dwarf galaxies but unlike stars in globular clusters.", "doi": "10.3847/1538-4357/aa6570", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2017-04-01", "series_number": "2", "volume": "838", "issue": "2", "pages": "Art. No. 83" }, { "id": "authors:09m3f-zem59", "collection": "authors", "collection_id": "09m3f-zem59", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170213-151130703", "type": "article", "title": "Chemistry and Kinematics of the Late-Forming Dwarf Irregular Galaxies Leo A, Aquarius, and Sagittarius DIG", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Rizzi", "given_name": "Luca", "orcid": "0000-0003-0882-2327", "clpid": "Rizzi-L" }, { "family_name": "Held", "given_name": "Enrico V.", "clpid": "Held-E-V" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Cole", "given_name": "Andrew A.", "orcid": "0000-0003-0303-3855", "clpid": "Cole-A-A" }, { "family_name": "Manning", "given_name": "Ellen M.", "clpid": "Manning-E-M" }, { "family_name": "Skillman", "given_name": "Evan D.", "clpid": "Skillman-E-D" }, { "family_name": "Weisz", "given_name": "Daniel R.", "orcid": "0000-0002-6442-6030", "clpid": "Weisz-D-R" } ], "abstract": "We present Keck/DEIMOS spectroscopy of individual stars in the relatively isolated Local Group dwarf galaxies Leo A, Aquarius, and the Sagittarius dwarf irregular galaxy. The three galaxies\u2014but especially Leo A and Aquarius\u2014share in common delayed star formation histories (SFHs) relative to many other isolated dwarf galaxies. The stars in all three galaxies are supported by dispersion. We found no evidence of stellar velocity structure, even for Aquarius, which has rotating H i gas. The velocity dispersions indicate that all three galaxies are dark-matter-dominated, with dark-to-baryonic mass ratios ranging from 4.4_(-0.8)^(+1.0) (SagDIG) to 9.6_(-1.8)^(+2.5) (Aquarius). Leo A and SagDIG have lower stellar metallicities than Aquarius, and they also have higher gas fractions, both of which would be expected if Aquarius were further along in its chemical evolution. The metallicity distribution of Leo A is inconsistent with a closed or leaky box model of chemical evolution, suggesting that the galaxy was pre-enriched or acquired external gas during star formation. The metallicities of stars increased steadily for all three galaxies, but possibly at different rates. The [\u03b1/Fe] ratios at a given [Fe/H] are lower than that of the Sculptor dwarf spheroidal galaxy, which indicates more extended SFHs than Sculptor, consistent with photometrically derived SFHs. Overall, the bulk kinematic and chemical properties for the late-forming dwarf galaxies do not diverge significantly from those of less delayed dwarf galaxies, including dwarf spheroidal galaxies.", "doi": "10.3847/1538-4357/834/1/9", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2017-01-01", "series_number": "1", "volume": "834", "issue": "1", "pages": "Art. No. 9" }, { "id": "authors:febay-0cf98", "collection": "authors", "collection_id": "febay-0cf98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170217-081936401", "type": "book_section", "title": "Prime Focus Spectrograph (PFS) for the Subaru Telescope: Overview, recent progress, and future perspectives", "book_title": "Ground-based and Airborne Instrumentation for Astronomy VI", "author": [ { "family_name": "Tamura", "given_name": "Naoyuki", "clpid": "Tamura-Naoyuki" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Dekany", "given_name": "Richard G.", "clpid": "Dekany-Richard" }, { "family_name": "Mao", "given_name": "Peter", "clpid": "Mao-Peter" }, { "family_name": "Reiley", "given_name": "Daniel J.", "clpid": "Reiley-D-J" }, { "family_name": "Roberts", "given_name": "Mitsuko", "clpid": "Roberts-Mitsuko" } ], "contributor": [ { "family_name": "Evans", "given_name": "Christopher J.", "clpid": "Evans-C-J" }, { "family_name": "Simard", "given_name": "Luc", "clpid": "Simard-L" }, { "family_name": "Takami", "given_name": "Hideki", "clpid": "Takami-Hideki" } ], "abstract": "PFS (Prime Focus Spectrograph), a next generation facility instrument on the 8.2-meter Subaru Telescope, is a very wide-field, massively multiplexed, optical and near-infrared spectrograph. Exploiting the Subaru prime focus, 2394 reconfigurable fibers will be distributed over the 1.3 deg field of view. The spectrograph has been designed with 3 arms of blue, red, and near-infrared cameras to simultaneously observe spectra from 380nm to 1260nm in one exposure at a resolution of ~1.6-2.7\u00c5. An international collaboration is developing this instrument under the initiative of Kavli IPMU. The project is now going into the construction phase aiming at undertaking system integration in 2017-2018 and subsequently carrying out engineering operations in 2018-2019. This article gives an overview of the instrument, current project status and future paths forward.", "doi": "10.1117/12.2232103", "isbn": "978-1-5106-0196-3", "publisher": "Society of Photo-Optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "2016-08-09", "pages": "Art. No. 99081M" }, { "id": "authors:dxx0h-hs287", "collection": "authors", "collection_id": "dxx0h-hs287", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160208-140133188", "type": "book_section", "title": "The Outer Galactic Halo As Probed By RR Lyr Stars From the Palomar Transient Facility + Keck", "book_title": "The General Assembly of Galaxy Halos: Structure, Origin and Evolution", "author": [ { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Banholzer", "given_name": "Sophianna", "clpid": "Banholzer-S" }, { "literal": "PTF Collaboration" } ], "contributor": [ { "family_name": "Bragaglia", "given_name": "Angela", "clpid": "Bragaglia-A" }, { "family_name": "Arnaboldi", "given_name": "Magda", "clpid": "Arnaboldi-M" }, { "family_name": "Rejkuba", "given_name": "Marina", "clpid": "Rejkuba-M" }, { "family_name": "Romano", "given_name": "Donatella", "clpid": "Romano-D" } ], "abstract": "We present initial results from our study of the outer halo of the Milky Way using a large sample of RR Lyr(ab) variables datamined from the archives of the Palomar Transient Facility. Of the 464 RR Lyr in our sample with distances exceeding 50 kpc, 62 have been observed spectroscopically at the Keck Observatory. v _r and \u03c3(v_r) are given as a function of distance between 50 and 110 kpc, and a very preliminary rather low total mass for the Milky Way out to 110 kpc of ~7 \u00b1 1.5 \u00d7 10^(11) M\u2299 is derived from our data.", "doi": "10.1017/S174392131500976X", "isbn": "9781107138193", "publisher": "Cambridge University Press", "place_of_publication": "Cambridge", "publication_date": "2016-05-09", "pages": "91-96" }, { "id": "authors:j6zpv-fmt22", "collection": "authors", "collection_id": "j6zpv-fmt22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160620-151853159", "type": "article", "title": "Serendipitous discovery of the faint solar twin Inti 1", "author": [ { "family_name": "Galarza", "given_name": "Jhon Yana", "clpid": "Galarza-J-Y" }, { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Context. Solar twins are increasingly the subject of many studies owing to their wide range of applications from testing stellar evolution models to the calibration of fundamental observables; these stars are also of interest because high precision abundances could be achieved that are key to investigating the chemical anomalies imprinted by planet formation. Furthermore, the advent of photometric surveys with large telescopes motivates the identification of faint solar twins in order to set the zero point of fundamental calibrations.\nAims. We intend to perform a detailed line-by-line differential analysis to verify whether 2MASS J23263267-0239363 (designated here as Inti 1) is indeed a solar twin.\nMethods. We determine the atmospheric parameters and differential abundances using high-resolution (R \u2248 50 000), high signal-to-noise (S/N \u2248 110\u2013240 per\u2009pixel) Keck/HIRES spectra for our solar twin candidate, the previously known solar twin HD 45184, and the Sun (using reflected light from the asteroid Vesta).\nResults. For the bright solar twin HD 45184, we found T_(eff) = 5864 \u00b1 9 K, log\u2009g = 4.45 \u00b1 0.03 dex, v_t = 1.11 \u00b1 0.02 km s^(-1), and [Fe/H] = 0.04 \u00b1 0.01 dex, which are in good agreement with previous works. Our abundances are in excellent agreement with a recent high-precision work, with an element-to-element scatter of only 0.01 dex. The star Inti 1 has atmospheric parameters T_(eff) = 5837 \u00b1 11 K, log\u2009g = 4.42 \u00b1 0.03 dex, v_t = 1.04 \u00b1 0.02 km s^(-1), and [Fe/H] = 0.07 \u00b1 0.01 dex that are higher than solar. The age and mass of the solar twin HD 45184 (3 Gyr and 1.05 M\u2299) and the faint solar twin Inti 1 (4 Gyr and 1.04 M\u2299) were estimated using isochrones. The differential analysis shows that HD 45184 presents an abundance pattern that is similar to typical nearby solar twins; this means this star has an enhanced refractory relative to volatile elements, while Inti 1 has an abundance pattern closer to solar, albeit somewhat enhanced in refractories. The abundance pattern of HD 45184 and Inti 1 could be reproduced by adding \u22483.5 M\u2295 and \u22481.5 M\u2295 of Earth-like material to the convective zone of the Sun.\nConclusions. The star Inti 1 is a faint solar twin, therefore, it could be used to calibrate the zero points of different photometric systems. The distant solar twin Inti 1 has an abundance pattern similar to the Sun with only a minor enhancement in the refractory elements. It would be important to analyze other distant solar twins to verify whether they share the Sun's abundance pattern or if they are enhanced in refractories, as is the case in the majority of nearby solar twins.", "doi": "10.1051/0004-6361/201527477", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2016-05", "volume": "589", "pages": "Art. No. A65" }, { "id": "authors:5ehhy-dyv76", "collection": "authors", "collection_id": "5ehhy-dyv76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160408-153111518", "type": "article", "title": "Lithium-Rich Giants in Globular Clusters", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Guhathakurta", "given_name": "Puragra", "orcid": "0000-0001-8867-4234", "clpid": "Guhathakurta-P" }, { "family_name": "Zhang", "given_name": "Andrew J.", "clpid": "Zhang-Andrew-J" }, { "family_name": "Hong", "given_name": "Jerry", "clpid": "Hong-Jerry" }, { "family_name": "Guo", "given_name": "Michelle", "clpid": "Guo-Michelle" }, { "family_name": "Guo", "given_name": "Rachel", "clpid": "Guo-Rachel" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Cunha", "given_name": "Katia", "clpid": "Cunha-K" } ], "abstract": "Although red giants deplete lithium on their surfaces, some giants are Li-rich. Intermediate-mass asymptotic giant branch (AGB) stars can generate Li through the Cameron\u2013Fowler conveyor, but the existence of Li-rich, low-mass red giant branch (RGB) stars is puzzling. Globular clusters are the best sites to examine this phenomenon because it is straightforward to determine membership in the cluster and to identify the evolutionary state of each star. In 72 hours of Keck/DEIMOS exposures in 25 clusters, we found four Li-rich RGB and two Li-rich AGB stars. There were 1696 RGB and 125 AGB stars with measurements or upper limits consistent with normal abundances of Li. Hence, the frequency of Li-richness in globular clusters is (0.2 \u00b1 0.1)% for the RGB, (1.6 \u00b1 1.1)% for the AGB, and (0.3 \u00b1 0.1)% for all giants. Because the Li-rich RGB stars are on the lower RGB, Li self-generation mechanisms proposed to occur at the luminosity function bump or He core flash cannot explain these four lower RGB stars. We propose the following origin for Li enrichment: (1) All luminous giants experience a brief phase of Li enrichment at the He core flash. (2) All post-RGB stars with binary companions on the lower RGB will engage in mass transfer. This scenario predicts that 0.1% of lower RGB stars will appear Li-rich due to mass transfer from a recently Li-enhanced companion. This frequency is at the lower end of our confidence interval.", "doi": "10.3847/0004-637X/819/2/135", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2016-03-10", "series_number": "2", "volume": "819", "issue": "2", "pages": "Art. No. 135" }, { "id": "authors:z3caj-b4492", "collection": "authors", "collection_id": "z3caj-b4492", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160226-075259066", "type": "article", "title": "Evidence of Fanning in the Ophiuchus Stream", "author": [ { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Price-Whelan", "given_name": "Adrian M.", "orcid": "0000-0003-0872-7098", "clpid": "Price-Whelan-A" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Rix", "given_name": "Hans-Walter", "orcid": "0000-0003-4996-9069", "clpid": "Rix-H-W" }, { "family_name": "Pearson", "given_name": "Sarah", "clpid": "Pearson-S" }, { "family_name": "Johnston", "given_name": "Kathryn V.", "orcid": "0000-0001-6244-6727", "clpid": "Johnston-K-V" }, { "family_name": "Bernard", "given_name": "Edouard J.", "clpid": "Bernard-E-J" }, { "family_name": "Ferguson", "given_name": "Annette M. N.", "clpid": "Ferguson-A-M-N" }, { "family_name": "Martin", "given_name": "Nicolas F.", "orcid": "0000-0002-1349-202X", "clpid": "Martin-N-F" }, { "family_name": "Slater", "given_name": "Colin T.", "clpid": "Slater-C-T" }, { "family_name": "Chambers", "given_name": "Kenneth C.", "orcid": "0000-0001-6965-7789", "clpid": "Chambers-K-C" }, { "family_name": "Flewelling", "given_name": "Heather", "orcid": "0000-0002-1050-4056", "clpid": "Flewelling-H" }, { "family_name": "Wainscoat", "given_name": "Richard J.", "orcid": "0000-0002-1341-0952", "clpid": "Wainscoat-R-J" }, { "family_name": "Waters", "given_name": "Christopher", "orcid": "0000-0003-1989-4879", "clpid": "Waters-C" } ], "abstract": "The Ophiuchus stellar stream presents a dynamical puzzle: its old stellar populations (~12 Gyr) cannot be reconciled with (1) its orbit in a simple model for the Milky Way potential and (2) its short angular extent, both of which imply that the observed stream formed within the last 230 km s^(\u22121)) against ~40 other stars: their velocities are comparable to those of the stream, but would be exceptional if they were unrelated halo stars. Their positions and velocities are, however, inconsistent with simple extrapolation of the observed cold, high-density portion of the stream. These observations suggest that stream-fanning may be a real, observable effect and, therefore, that Ophiuchus may be on a chaotic orbit. They also show that the Ophiuchus stream is more extended and hence dynamically older than previously thought, easing the stellar population versus dynamical age tension.", "doi": "10.3847/2041-8205/816/1/L4", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2016-01-01", "series_number": "1", "volume": "816", "issue": "1", "pages": "Art. No.L4" }, { "id": "authors:cyvd9-9ds07", "collection": "authors", "collection_id": "cyvd9-9ds07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151118-093653068", "type": "article", "title": "Triangulum II: Possibly a Very Dense Ultra-faint Dwarf Galaxy", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Simon", "given_name": "Joshua D.", "clpid": "Simon-J-D" }, { "family_name": "Guhathakurta", "given_name": "Puragra", "orcid": "0000-0001-8867-4234", "clpid": "Guhathakurta-P" } ], "abstract": "Laevens et al. recently discovered Triangulum II (Tri II), a satellite of the Milky Way. Its Galactocentric distance is 36 kpc, and its luminosity is only 450 L_\u2299. Using Keck/DEIMOS, we measured the radial velocities of six member stars within 1'.2 of the center of Tri II, and we found a velocity dispersion of \u03c3_v = 5.1_(-1.4)^(+4.0) km s^(-1). We also measured the metallicities of three stars and found a range of 0.8 dex in [Fe/H]. The velocity and metallicity dispersions identify Tri II as a dark matter-dominated galaxy. The galaxy is moving very quickly toward the Galactic center v_(GSR) = -262 km s^(-1). Although it might be in the process of being tidally disrupted as it approaches pericenter, there is no strong evidence for disruption in our data set. The ellipticity is low, and the mean velocity, \u3008|v_(helio)\u3009 =-382.1 \u00b1 2.9 km s^(-1), rules out an association with the Triangulum\u2013Andromeda substructure or the Pan-Andromeda Archaeological Survey stellar stream. If Tri II is in dynamical equilibrium, then it would have a mass-to-light ratio of 3600_(-2100)^(+3500) M}_\u2299 L_\u2299^(-1), the highest of any non-disrupting galaxy (those for which dynamical mass estimates are reliable). The density within the 3D half-light radius would be 4.8_(-3.5)^(+8.1) M\u2299 pc^(-3), even higher than Segue 1. Hence, Tri II is an excellent candidate for the indirect detection of dark matter annihilation.", "doi": "10.1088/2041-8205/814/1/L7", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2015-11-20", "series_number": "1", "volume": "814", "issue": "1", "pages": "Art. No. L7" }, { "id": "authors:zzd1q-z5060", "collection": "authors", "collection_id": "zzd1q-z5060", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150615-053227138", "type": "article", "title": "Spectroscopic Confirmation of the Dwarf Galaxies Hydra II and Pisces II and the Globular Cluster Laevens 1", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Simon", "given_name": "Joshua D.", "clpid": "Simon-J-D" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present Keck/DEIMOS spectroscopy of stars in the recently discovered Milky Way satellites Hydra II, Pisces II, and Laevens 1. We measured a velocity dispersion of 5.4^(+3.6)_(-2.4) km s^(\u22121) for Pisces II, but we did not resolve the velocity dispersions of Hydra II or Laevens 1. We marginally resolved the metallicity dispersions of Hydra II and Pisces II but not Laevens 1. Furthermore, Hydra II and Pisces II obey the luminosity\u2013metallicity relation for Milky Way dwarf galaxies (\u3008[Fe/H] \u3009 = -2.02 \u00b1 0.08 and -2.45 \u00b1 0.07, respectively), whereas Laevens 1 does not (\u3008[Fe/H]\u3009= -1.68 \u00b1 0.05). The kinematic and chemical properties suggest that Hydra II and Pisces II are dwarf galaxies, and Laevens 1 is a globular cluster. We determined that two of the previously observed blue stars near the center of Laevens 1 are not members of the cluster. A third blue star has ambiguous membership. Hydra II has a radial velocity \u3008\u03bd_(helio) \u3009 = 303.1 \u00b1 1.4 km s^(\u22121), similar to the leading arm of the Magellanic stream. The mass-to-light ratio for Pisces II is 370^(+310)_(-240) M\u2299/L\u2299. It is not among the most dark matter-dominated dwarf galaxies, but it is still worthy of inclusion in the search for gamma-rays from dark matter self-annihilation.", "doi": "10.1088/0004-637X/810/1/56", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2015-09-01", "series_number": "1", "volume": "810", "issue": "1", "pages": "Art. No. 56" }, { "id": "authors:cj9qt-65a20", "collection": "authors", "collection_id": "cj9qt-65a20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20151020-095138179", "type": "article", "title": "The Nature and Orbit of the Ophiuchus Stream", "author": [ { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Bovy", "given_name": "Jo", "clpid": "Bovy-J" }, { "family_name": "Bernard", "given_name": "Edouard J.", "clpid": "Bernard-E-J" }, { "family_name": "Caldwell", "given_name": "Nelson", "clpid": "Caldwell-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Fouesneau", "given_name": "Morgan", "clpid": "Fouesneau-M" }, { "family_name": "Johnson", "given_name": "Christian I.", "clpid": "Johnson-C-I" }, { "family_name": "Ness", "given_name": "Melissa", "orcid": "0000-0001-5082-6693", "clpid": "Ness-M-K" }, { "family_name": "Ferguson", "given_name": "Annette M. N.", "clpid": "Ferguson-A-M-N" }, { "family_name": "Martin", "given_name": "Nicolas F.", "orcid": "0000-0002-1349-202X", "clpid": "Martin-N-F" }, { "family_name": "Price-Whelan", "given_name": "Adrian M.", "orcid": "0000-0003-0872-7098", "clpid": "Price-Whelan-A" }, { "family_name": "Rix", "given_name": "Hans-Walter", "orcid": "0000-0003-4996-9069", "clpid": "Rix-H-W" }, { "family_name": "Schlafly", "given_name": "Edward F.", "orcid": "0000-0002-3569-7421", "clpid": "Schlafly-E-F" }, { "family_name": "Burgett", "given_name": "William S.", "clpid": "Burgett-W-S" }, { "family_name": "Chambers", "given_name": "Kenneth C.", "orcid": "0000-0001-6965-7789", "clpid": "Chambers-K-C" }, { "family_name": "Flewelling", "given_name": "Heather", "orcid": "0000-0002-1050-4056", "clpid": "Flewelling-H" }, { "family_name": "Hodapp", "given_name": "Klaus W.", "orcid": "0000-0003-0786-2140", "clpid": "Hodapp-K-W" }, { "family_name": "Kaiser", "given_name": "Nick", "orcid": "0000-0001-6511-4306", "clpid": "Kaiser-N" }, { "family_name": "Magnier", "given_name": "Eugene A.", "orcid": "0000-0002-7965-2815", "clpid": "Magnier-E-A" }, { "family_name": "Platais", "given_name": "Imants", "clpid": "Platais-I" }, { "family_name": "Tonry", "given_name": "John L.", "orcid": "0000-0003-2858-9657", "clpid": "Tonry-J-L" }, { "family_name": "Waters", "given_name": "Christopher", "orcid": "0000-0003-1989-4879", "clpid": "Waters-C" }, { "family_name": "Wyse", "given_name": "Rosemary F. G.", "clpid": "Wyse-R-F-G" } ], "abstract": "The Ophiuchus stream is a recently discovered stellar tidal stream in the Milky Way. We present high-quality spectroscopic data for 14 stream member stars obtained using the Keck and MMT telescopes. We confirm the stream as a fast moving (v_(los) ~ 290 km s^(\u22121)), kinematically cold group (\u03c3 _(v_(los)) \u227e 1 km s^(\u22121)) of \u03b1-enhanced and metal-poor stars ([\u03b1/Fe] ~ 0.4 dex, [Fe/H] ~ \u22122.0 dex). Using a probabilistic technique, we model the stream simultaneously in line-of-sight velocity, color\u2013magnitude, coordinate, and proper motion space, and so determine its distribution in 6D phase-space. We find that the stream extends in distance from 7.5 to 9 kpc from the Sun; it is 50 times longer than wide, merely appearing highly foreshortened in projection. The analysis of the stellar population contained in the stream suggests that it is ~12 Gyr old, and that its initial stellar mass was ~2 \u00d7 10^4 M\u2299 (or at least \u22737 \u00d7 10^3 M\u2299). Assuming a fiducial Milky Way potential, we fit an orbit to the stream that matches the observed phase-space distribution, except for some tension in the proper motions: the stream has an orbital period of ~350 Myr, and is on a fairly eccentric orbit (e ~ 0.66) with a pericenter of ~3.5 kpc and an apocenter of ~17 kpc. The phase-space structure and stellar population of the stream show that its progenitor must have been a globular cluster that was disrupted only ~240 Myr ago. We do not detect any significant overdensity of stars along the stream that would indicate the presence of a progenitor, and conclude that the stream is all that is left of the progenitor.", "doi": "10.1088/0004-637X/809/1/59", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2015-08-10", "series_number": "1", "volume": "809", "issue": "1", "pages": "Art. No. 59" }, { "id": "authors:95p4h-jc690", "collection": "authors", "collection_id": "95p4h-jc690", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150201-144307311", "type": "article", "title": "Carbon in Red Giants in Globular Clusters and Dwarf Spheroidal Galaxies", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Guo", "given_name": "Michelle", "clpid": "Guo-Michelle" }, { "family_name": "Zhang", "given_name": "Andrew J.", "clpid": "Zhang-Andrew-J" }, { "family_name": "Deng", "given_name": "Michelle", "clpid": "Deng-Michelle" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Guhathakurta", "given_name": "Puragra", "orcid": "0000-0001-8867-4234", "clpid": "Guhathakurta-P" }, { "family_name": "Shetrone", "given_name": "Matthew D.", "clpid": "Shetrone-M-D" }, { "family_name": "Lee", "given_name": "Young Sun", "clpid": "Lee-Young-Sun" }, { "family_name": "Rizzi", "given_name": "Luca", "orcid": "0000-0003-0882-2327", "clpid": "Rizzi-L" } ], "abstract": "We present carbon abundances of red giants in Milky Way globular clusters and dwarf spheroidal galaxies (dSphs). Our sample includes measurements of carbon abundances for 154 giants in the clusters NGC 2419, M68, and M15 and 398 giants in the dSphs Sculptor, Fornax, Ursa Minor, and Draco. This sample doubles the number of dSph stars with measurements of [C/Fe]. The [C/Fe] ratio in the clusters decreases with increasing luminosity above log(L/L_\u2299)\u22431.6, which can be explained by deep mixing in evolved giants. The same decrease is observed in dSphs, but the initial [C/Fe] of the dSph giants is not uniform. Stars in dSphs at lower metallicities have larger [C/Fe] ratios. We hypothesize that [C/Fe] (corrected to the initial carbon abundance) declines with increasing [Fe/H] due to the metallicity dependence of the carbon yield of asymptotic giant branch stars and due to the increasing importance of Type Ia supernovae at higher metallicities. We also identified 11 very carbon-rich giants (8 previously known) in three dSphs. However, our selection biases preclude a detailed comparison to the carbon-enhanced fraction of the Milky Way stellar halo. Nonetheless, the stars with [C/Fe] < +1 in dSphs follow a different [C/Fe] track with [Fe/H] than the halo stars. Specifically, [C/Fe] in dSphs begins to decline at lower [Fe/H] than in the halo. The difference in the metallicity of the [C/Fe] \"knee\" adds to the evidence from [\u03b1/Fe] distributions that the progenitors of the halo had a shorter timescale for chemical enrichment than the surviving dSphs.", "doi": "10.1088/0004-637X/801/2/125", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2015-03-10", "series_number": "2", "volume": "801", "issue": "2", "pages": "Art. No. 125" }, { "id": "authors:ght8j-k5q83", "collection": "authors", "collection_id": "ght8j-k5q83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150115-104353320", "type": "article", "title": "The Detailed Chemical Properties of M31 Star Clusters. I. Fe, Alpha and Light Elements", "author": [ { "family_name": "Colucci", "given_name": "Janet E.", "clpid": "Colucci-J-E" }, { "family_name": "Bernstein", "given_name": "Rebecca A.", "clpid": "Bernstein-R-A" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present ages, Fe/H] and abundances of the a elements Ca I, Si I, Ti I, Ti II, and light elements Mg I, Na I, and Al I for 31 globular clusters (GCs) in M31, which were obtained from high-resolution, high signal-to-noise ratio > 60 echelle spectra of their integrated light (IL). All abundances and ages are obtained using our original technique for high-resolution IL abundance analysis of GCs. This sample provides a never before seen picture of the chemical history of M31. The GCs are dispersed throughout the inner and outer halo, from 2.5 kpc < R_(M31) < 117 kpc. We find a range of Fe/H] within 20 kpc of the center of M31, and a constant Fe/H] ~-1.6 for the outer halo clusters. We find evidence for at least one massive GC in M31 with an age between 1 and 5 Gyr. The \u0251-element ratios are generally similar to the Milky Way GC and field star ratios. We also find chemical evidence for a late-time accretion origin for at least one cluster, which has a different abundance pattern than other clusters at similar metallicity. We find evidence for star-to-star abundance variations in Mg, Na, and Al in the GCs in our sample, and find correlations of Ca, Mg, Na, and possibly Al abundance ratios with cluster luminosity and velocity dispersion, which can potentially be used to constrain GC self-enrichment scenarios. Data presented here were obtained with the HIRES echelle spectrograph on the Keck I telescope.", "doi": "10.1088/0004-637X/797/2/116", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2014-12-20", "series_number": "2", "volume": "797", "issue": "2", "pages": "Art. No. 116" }, { "id": "authors:9dt52-2nf98", "collection": "authors", "collection_id": "9dt52-2nf98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141016-152037601", "type": "article", "title": "Stacking the Invisibles: A Guided Search for Low-Luminosity Milky Way Satellites", "author": [ { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Banholzer", "given_name": "Sophianna R.", "clpid": "Banholzer-S-R" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Martin", "given_name": "Nicolas F.", "orcid": "0000-0002-1349-202X", "clpid": "Martin-N-F" }, { "family_name": "Grillmair", "given_name": "Carl J.", "orcid": "0000-0003-4072-169X", "clpid": "Grillmair-C-J" }, { "family_name": "Levitan", "given_name": "David", "clpid": "Levitan-D" }, { "family_name": "Laher", "given_name": "Russ R.", "orcid": "0000-0003-2451-5482", "clpid": "Laher-R-R" }, { "family_name": "Ofek", "given_name": "Eran O.", "orcid": "0000-0002-6786-8774", "clpid": "Ofek-E-O" }, { "family_name": "Surace", "given_name": "Jason A.", "orcid": "0000-0001-7291-0087", "clpid": "Surace-J-A" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Prince", "given_name": "Thomas A.", "orcid": "0000-0002-8850-3627", "clpid": "Prince-T-A" }, { "family_name": "Rix", "given_name": "Hans-Walter", "orcid": "0000-0003-4996-9069", "clpid": "Rix-H-W" } ], "abstract": "Almost every known low-luminosity Milky Way dwarf spheroidal (dSph) satellite galaxy contains at least one RR Lyrae star. Assuming that a fraction of distant (60 < d _(helio) < 100 kpc) Galactic halo RR Lyrae stars are members of yet to be discovered low-luminosity dSph galaxies, we perform a guided search for these low-luminosity dSph galaxies. In order to detect the presence of dSph galaxies, we combine stars selected from more than 123 sightlines centered on RR Lyrae stars identified by the Palomar Transient Factory. We find that this method is sensitive enough to detect the presence of Segue 1-like galaxies (M_V= -1.5^(+0.6)_(-0.8), r_h = 30 pc) even if only ~20 sightlines were occupied by such dSph galaxies. Yet, when our method is applied to the Sloan Digital Sky Survey Data Release 10 imaging catalog, no signal is detected. An application of our method to sightlines occupied by pairs of close (<200 pc) horizontal branch stars, also did not yield a detection. Thus, we place upper limits on the number of low-luminosity dSph galaxies with half-light radii from 30 pc to 120 pc, and in the probed volume of the halo. Stronger constraints on the luminosity function may be obtained by applying our method to sightlines centered on RR Lyrae stars selected from the Pan-STARRS1 survey, and eventually, from the Large Synoptic Survey Telescope. In Appendix A, we present spectroscopic observations of an RRab star in the Bo\u00f6tes 3 dSph and a light curve of an RRab star near the Bo\u00f6tes 2 dSph.", "doi": "10.1088/0004-637X/793/2/135", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2014-10-01", "series_number": "2", "volume": "793", "issue": "2", "pages": "Art. No. 135" }, { "id": "authors:w5ggt-chk46", "collection": "authors", "collection_id": "w5ggt-chk46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20141003-093421671", "type": "article", "title": "A Continuum of H- to He-Rich Tidal Disruption Candidates With a Preference for E+A Galaxies", "author": [ { "family_name": "Arcavi", "given_name": "Iair", "orcid": "0000-0001-7090-4898", "clpid": "Arcavi-I" }, { "family_name": "Yan", "given_name": "Lin", "orcid": "0000-0003-1710-9339", "clpid": "Yan-Lin" }, { "family_name": "Yang", "given_name": "Chen-Wei", "clpid": "Yang-Chen-Wei" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Tendulkar", "given_name": "Shriharsh P.", "orcid": "0000-0003-2548-2926", "clpid": "Tendulkar-S-P" }, { "family_name": "Tang", "given_name": "Sumin", "orcid": "0000-0002-6225-8918", "clpid": "Tang-Sumin" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Perley", "given_name": "Daniel A.", "orcid": "0000-0001-8472-1996", "clpid": "Perley-D-A" }, { "family_name": "Miller", "given_name": "Adam A.", "orcid": "0000-0001-9515-478X", "clpid": "Miller-A-A" }, { "family_name": "Laher", "given_name": "Russ R.", "orcid": "0000-0003-2451-5482", "clpid": "Laher-R-R" }, { "family_name": "Kasliwal", "given_name": "M. M.", "orcid": "0000-0002-5619-4938", "clpid": "Kasliwal-M-M" } ], "abstract": "We present the results of a Palomar Transient Factory (PTF) archival search for blue transients that lie in the magnitude range between \"normal\" core-collapse and superluminous supernovae (i.e., with \u201321 \u2264 M_(R (peak)) \u2264 \u2013 19). Of the six events found after excluding all interacting Type IIn and Ia-CSM supernovae, three (PTF09ge, 09axc, and 09djl) are coincident with the centers of their hosts, one (10iam) is offset from the center, and a precise offset cannot be determined for two (10nuj and 11glr). All the central events have similar rise times to the He-rich tidal disruption candidate PS1-10jh, and the event with the best-sampled light curve also has similar colors and power-law decay. Spectroscopically, PTF09ge is He-rich, while PTF09axc and 09djl display broad hydrogen features around peak magnitude. All three central events are in low star formation hosts, two of which are E+A galaxies. Our spectrum of the host of PS1-10jh displays similar properties. PTF10iam, the one offset event, is different photometrically and spectroscopically from the central events, and its host displays a higher star formation rate. Finding no obvious evidence for ongoing galactic nuclei activity or recent star formation, we conclude that the three central transients likely arise from the tidal disruption of a star by a supermassive black hole. We compare the spectra of these events to tidal disruption candidates from the literature and find that all of these objects can be unified on a continuous scale of spectral properties. The accumulated evidence of this expanded sample strongly supports a tidal disruption origin for this class of nuclear transients.", "doi": "10.1088/0004-637X/793/1/38", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2014-09-20", "series_number": "1", "volume": "793", "issue": "1", "pages": "Art. No. 38" }, { "id": "authors:kgcjc-aqr02", "collection": "authors", "collection_id": "kgcjc-aqr02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140911-134416477", "type": "article", "title": "Multi-epoch high-spectral-resolution observations of neutral sodium in 14 Type Ia supernovae", "author": [ { "family_name": "Sternberg", "given_name": "A.", "clpid": "Sternberg-A" }, { "family_name": "Gal-Yam", "given_name": "A.", "orcid": "0000-0002-3653-5598", "clpid": "Gal-Yam-A" }, { "family_name": "Simon", "given_name": "J. D.", "clpid": "Simon-J-D" }, { "family_name": "Patat", "given_name": "F.", "orcid": "0000-0002-0537-3573", "clpid": "Patat-F" }, { "family_name": "Hillebrandt", "given_name": "W.", "clpid": "Hillebrandt-W" }, { "family_name": "Phillips", "given_name": "M. M.", "orcid": "0000-0003-2734-0796", "clpid": "Phillips-M-M" }, { "family_name": "Foley", "given_name": "R. J.", "clpid": "Foley-R-J" }, { "family_name": "Thompson", "given_name": "I.", "clpid": "Thompson-I-B" }, { "family_name": "Morrell", "given_name": "N.", "orcid": "0000-0003-2535-3091", "clpid": "Morrell-N" }, { "family_name": "Chomiuk", "given_name": "L.", "orcid": "0000-0002-8400-3705", "clpid": "Chomiuk-L" }, { "family_name": "Soderberg", "given_name": "A. M.", "clpid": "Soderberg-A-M" }, { "family_name": "Yong", "given_name": "D.", "clpid": "Yong-D" }, { "family_name": "Kraus", "given_name": "A. L.", "orcid": "0000-0001-9811-568X", "clpid": "Kraus-A-L" }, { "family_name": "Herczeg", "given_name": "G. J.", "orcid": "0000-0002-7154-6065", "clpid": "Herczeg-G-J" }, { "family_name": "Hsiao", "given_name": "E. Y.", "clpid": "Hsiao-Eric-Y-Astro" }, { "family_name": "Raskutti", "given_name": "S.", "clpid": "Raskutti-S" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Mazzali", "given_name": "P. A.", "orcid": "0000-0001-6876-8284", "clpid": "Mazzali-P-A" }, { "family_name": "Nomoto", "given_name": "K.", "orcid": "0000-0001-9553-0685", "clpid": "Nomoto-Ken'ichi" } ], "abstract": "One of the main questions concerning Type Ia supernovae is the nature of the binary companion of the exploding white dwarf. A major discriminant between different suggested models is the presence and physical properties of circumstellar material at the time of explosion. If present, this material will be ionized by the ultraviolet radiation of the explosion and later recombine. This ionization\u2013recombination should manifest itself as time-variable absorption features that can be detected via multi-epoch high-spectral-resolution observations. Previous studies have shown that the strongest effect is seen in the neutral sodium D lines. We report on observations of neutral sodium absorption features observed in multi-epoch high-resolution spectra of 14 Type Ia supernova events. This is the first multi-epoch high-resolution study to include multiple SNe. No variability in line strength that can be associated with circumstellar material is detected in the events presented in this paper. If we include previously published events, we find that \u223c18 per cent of the events in the extended sample exhibit time-variable sodium features associated with circumstellar material. We explore the implication of this study on our understanding of the progenitor systems of Type Ia supernovae via the current Type Ia supernova multi-epoch high-spectral-resolution sample.", "doi": "10.1093/mnras/stu1202", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2014-09-11", "series_number": "2", "volume": "443", "issue": "2", "pages": "1849-1860" }, { "id": "authors:xp2xm-6j918", "collection": "authors", "collection_id": "xp2xm-6j918", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140424-141430731", "type": "article", "title": "The dynamics of isolated Local Group galaxies", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Bullock", "given_name": "James S.", "orcid": "0000-0003-4298-5082", "clpid": "Bullock-J-S" }, { "family_name": "Boylan-Kolchin", "given_name": "Michael", "orcid": "0000-0002-9604-343X", "clpid": "Boylan-Kolchin-M" }, { "family_name": "Kaplinghat", "given_name": "Manoj", "clpid": "Kaplinghat-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We measured velocities of 862 individual red giant stars in seven isolated dwarf galaxies in the Local Group: NGC 6822, IC 1613, VV 124 (UGC 4879), the Pegasus dwarf irregular galaxy (DDO 216), Leo A, Cetus and Aquarius (DDO 210). We also computed velocity dispersions, taking into account the measurement uncertainties on individual stars. None of the isolated galaxies is denser than the densest Local Group satellite galaxy. Furthermore, the isolated dwarf galaxies have no obvious distinction in the velocity dispersion\u2013half-light radius plane from the satellite galaxies of the Milky Way and M31. The similarity of the isolated and satellite galaxies' dynamics and structural parameters imposes limitations on environmental solutions to the 'too big to fail' problem, wherein there are fewer dense dwarf satellite galaxies than would be expected from cold dark matter simulations. This data set also has many other applications for dwarf galaxy evolution, including the transformation of dwarf irregular into dwarf spheroidal galaxies. We intend to explore these issues in future work.", "doi": "10.1093/mnras/stu025", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2014-03-21", "series_number": "1", "volume": "439", "issue": "1", "pages": "1015-1027" }, { "id": "authors:dx8p3-k2z24", "collection": "authors", "collection_id": "dx8p3-k2z24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140121-091543595", "type": "article", "title": "The Universal Stellar Mass-Stellar Metallicity Relation for Dwarf Galaxies", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Guhathakurta", "given_name": "Puragra", "orcid": "0000-0001-8867-4234", "clpid": "Guhathakurta-P" }, { "family_name": "Cheng", "given_name": "Lucy", "clpid": "Cheng-Lucy" }, { "family_name": "Bullock", "given_name": "James S.", "orcid": "0000-0003-4298-5082", "clpid": "Bullock-J-S" }, { "family_name": "Gallazzi", "given_name": "Anna", "clpid": "Gallazzi-A" } ], "abstract": "We present spectroscopic metallicities of individual stars in seven gas-rich dwarf irregular galaxies (dIrrs), and we show that dIrrs obey the same mass-metallicity relation as the dwarf spheroidal (dSph) satellites of both the Milky Way and M31: Z_* \u221d M_*^(0.30\u00b10.02). The uniformity of the relation is in contradiction to previous estimates of metallicity based on photometry. This relationship is roughly continuous with the stellar mass-stellar metallicity relation for galaxies as massive as M_* = 10^(12) M_\u2609. Although the average metallicities of dwarf galaxies depend only on stellar mass, the shapes of their metallicity distributions depend on galaxy type. The metallicity distributions of dIrrs resemble simple, leaky box chemical evolution models, whereas dSphs require an additional parameter, such as gas accretion, to explain the shapes of their metallicity distributions. Furthermore, the metallicity distributions of the more luminous dSphs have sharp, metal-rich cut-offs that are consistent with the sudden truncation of star formation due to ram pressure stripping.", "doi": "10.1088/0004-637X/779/2/102", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2013-12-20", "series_number": "2", "volume": "779", "issue": "2", "pages": "Art. No. 102" }, { "id": "authors:3b1vz-k3234", "collection": "authors", "collection_id": "3b1vz-k3234", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131224-070301937", "type": "article", "title": "Normal and Outlying Populations of the Milky Way Stellar Halo at [Fe/H] < \u20132", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Shectman", "given_name": "Stephen", "clpid": "Shectman-S" }, { "family_name": "Reimers", "given_name": "Dieter", "clpid": "Reimers-D" }, { "family_name": "Wisotzki", "given_name": "Lutz", "clpid": "Wisotzki-L" }, { "family_name": "Kirby", "given_name": "Evan", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" } ], "abstract": "From detailed abundance analysis of >100 Hamburg/ESO candidate extremely metal-poor (EMP) stars we find 45 with [Fe/H] < \u20133.0 dex. We identify a heretofore unidentified group: Ca-deficient stars with sub-solar [Ca/Fe] ratios and the lowest neutron-capture abundances; the Ca-deficient group comprises ~10% of the sample, excluding Carbon stars. Our radial velocity distribution shows that the carbon-enhanced stars with no s-process enhancements, CEMP-no, and which do not show C2 bands are not preferentially binary systems. Ignoring Carbon stars, approximately 15% of our sample are strong (\u22655\u03c3) outliers in one or more elements between Mg and Ni; this rises to ~19% if very strong (\u226510\u03c3) outliers for Sr and Ba are included. Examples include: HE0305\u20130554 with the lowest [Ba/H] known; HE1012\u20131540 and HE2323\u20130256, two (non-velocity variable) C-rich stars with very strong [Mg,Al/Fe] enhancements; and HE1226\u20131149, an extremely r-process rich star.", "doi": "10.1088/0004-637X/778/1/56", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2013-11-20", "series_number": "1", "volume": "778", "issue": "1", "pages": "Art. No. 56" }, { "id": "authors:cz9cf-jhx34", "collection": "authors", "collection_id": "cz9cf-jhx34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191023-154321407", "type": "article", "title": "Tracing the Orphan Stream to 55 kpc with RR Lyrae Stars", "author": [ { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Grillmair", "given_name": "Carl J.", "orcid": "0000-0003-4072-169X", "clpid": "Grillmair-C-J" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Bellm", "given_name": "Eric C.", "orcid": "0000-0001-8018-5348", "clpid": "Bellm-E-C" }, { "family_name": "Bhalerao", "given_name": "Varun B.", "orcid": "0000-0002-6112-7609", "clpid": "Bhalerao-V-B" }, { "family_name": "Levitan", "given_name": "David", "clpid": "Levitan-D-B" }, { "family_name": "Laher", "given_name": "Russ R.", "orcid": "0000-0003-2451-5482", "clpid": "Laher-R-R" }, { "family_name": "Ofek", "given_name": "Eran O.", "orcid": "0000-0002-6786-8774", "clpid": "Ofek-E-O" }, { "family_name": "Surace", "given_name": "Jason A.", "orcid": "0000-0001-7291-0087", "clpid": "Surace-J-A" }, { "family_name": "Tang", "given_name": "Sumin", "orcid": "0000-0002-6225-8918", "clpid": "Tang-Sumin" }, { "family_name": "Waszczak", "given_name": "Adam", "clpid": "Waszczak-A" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Prince", "given_name": "Thomas A.", "orcid": "0000-0002-8850-3627", "clpid": "Prince-T-A" } ], "abstract": "We report positions, velocities and metallicities of 50 ab-type RR Lyrae (RRab) stars observed in the\nvicinity of the Orphan stellar stream. Using about 30 RRab stars classified as being likely members\nof the Orphan stream, we study the metallicity and the spatial extent of the stream. We find that\nRRab stars in the Orphan stream have a wide range of metallicities, from -1.5 dex to -2.7 dex. The\naverage metallicity of the stream is -2.1 dex, identical to the value obtained by Newberg et al. (2010)\nusing blue horizontal branch stars. We find that the most distant parts of the stream (40-50 kpc from\nthe Sun) are about 0.3 dex more metal-poor than the closer parts (within ~ 30 kpc), suggesting a\npossible metallicity gradient along the stream's length. We have extended the previous studies and\nhave mapped the stream up to 55 kpc from the Sun. Even after a careful search, we did not identify\nany more distant RRab stars that could plausibly be members of the Orphan stream. If confirmed\nwith other tracers, this result would indicate a detection of the end of the leading arm of the stream.\nWe have compared the distances of Orphan stream RRab stars with the best-fit orbits obtained by\nNewberg et al. (2010). We find that model 6 of Newberg et al. (2010) cannot explain the distances\nof the most remote Orphan stream RRab stars, and conclude that the best fit to distances of Orphan\nstream RRab stars and to the local circular velocity is provided by potentials where the total mass\nof the Galaxy within 60 kpc is M_(60) ~ 2.7 x 10^(11) M_\u2299, or about 60% of the mass found by previous\nstudies. More extensive modelling that would consider non-spherical potentials and the possibility of\nmisalignment between the stream and the orbit, is highly encouraged.", "doi": "10.1088/0004-637X/776/1/26", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2013-10-10", "series_number": "1", "volume": "776", "issue": "1", "pages": "Art. No. 26" }, { "id": "authors:nk67v-1zg02", "collection": "authors", "collection_id": "nk67v-1zg02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131024-141234863", "type": "article", "title": "The Origin of HVS17, an Unbound Main Sequence B Star at 50 kpc", "author": [ { "family_name": "Brown", "given_name": "Warren R.", "clpid": "Brown-W-R" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Geller", "given_name": "Margaret J.", "clpid": "Geller-M-J" }, { "family_name": "Kenyon", "given_name": "Scott J.", "orcid": "0000-0003-0214-609X", "clpid": "Kenyon-S-J" } ], "abstract": "We analyze Keck Echellette Spectrograph and Imager spectroscopy of HVS17, a B-type star traveling with a Galactic rest frame radial velocity of +445 km s^(\u22121) in the outer halo of the Milky Way. HVS17 has the projected rotation of a main sequence B star and is chemically peculiar, with solar iron abundance and sub-solar alpha abundance. Comparing measured T_(eff) and log\u2009g with stellar evolution tracks implies that HVS17 is a 3.91 \u00b1 0.09 M_\u2609, 153 \u00b1 9 Myr old star at a Galactocentric distance of r = 48.5 \u00b1 4.6 kpc. The time between its formation and ejection significantly exceeds 10 Myr and thus is difficult to reconcile with any Galactic disk runaway scenario involving massive stars. The observations are consistent, on the other hand, with a hypervelocity star ejection from the Galactic center. We show that Gaia proper motion measurements will easily discriminate between a disk and Galactic center origin, thus allowing us to use HVS17 as a test particle to probe the shape of the Milky Way's dark matter halo.", "doi": "10.1088/0004-637X/775/1/32", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2013-09-20", "series_number": "1", "volume": "775", "issue": "1", "pages": "Art. No. 32" }, { "id": "authors:cssvm-2d004", "collection": "authors", "collection_id": "cssvm-2d004", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130924-092209940", "type": "article", "title": "Metal Abundances, Radial Velocities, and Other Physical Characteristics for the RR Lyrae Stars in The Kepler Field", "author": [ { "family_name": "Nemec", "given_name": "James M.", "clpid": "Nemec-J-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Ripepi", "given_name": "Vincenzo", "clpid": "Ripepi-V" }, { "family_name": "Derekas", "given_name": "Aliz", "orcid": "0000-0002-6526-9444", "clpid": "Derekas-A" }, { "family_name": "Moskalik", "given_name": "Pawel", "clpid": "Moskalik-P" }, { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Chadid", "given_name": "Merieme", "clpid": "Chadid-M" }, { "family_name": "Bruntt", "given_name": "Hans", "clpid": "Bruntt-H" } ], "abstract": "Spectroscopic iron-to-hydrogen ratios, radial velocities, atmospheric parameters, and new photometric analyses are presented for 41 RR Lyrae stars (and one probable high-amplitude \u03b4 Sct star) located in the field-of-view of the Kepler space telescope. Thirty-seven of the RR Lyrae stars are fundamental-mode pulsators (i.e., RRab stars) of which sixteen exhibit the Blazhko effect. Four of the stars are multiperiodic RRc pulsators oscillating primarily in the first-overtone mode. Spectroscopic [Fe/H] values for the 34 stars for which we were able to derive estimates range from \u20132.54 \u00b1 0.13 (NR Lyr) to \u20130.05 \u00b1 0.13 dex (V784 Cyg), and for the 19 Kepler-field non-Blazhko stars studied by Nemec et al. the abundances agree will with their photometric [Fe/H] values. Four non-Blazhko RR Lyrae stars that they identified as metal-rich (KIC 6100702, V2470 Cyg, V782 Cyg and V784 Cyg) are confirmed as such, and four additional stars (V839 Cyg, KIC 5520878, KIC 8832417, KIC 3868420) are also shown here to be metal-rich. Five of the non-Blazhko RRab stars are found to be more metal-rich than [Fe/H] ~\u20130.9 dex while all of the 16 Blazhko stars are more metal-poor than this value. New P-\u00d8_(31)^s-[Fe/H] relationships are derived based on ~970 days of quasi-continuous high-precision Q0-Q11 long- and short-cadence Kepler photometry. With the exception of some Blazhko stars, the spectroscopic and photometric [Fe/H] values are in good agreement. Several stars with unique photometric characteristics are identified, including a Blazhko variable with the smallest known amplitude and frequency modulations (V838 Cyg).", "doi": "10.1088/0004-637X/773/2/181", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2013-08-20", "series_number": "2", "volume": "773", "issue": "2", "pages": "Art. No. 181" }, { "id": "authors:zm0bb-maw06", "collection": "authors", "collection_id": "zm0bb-maw06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130723-132136704", "type": "article", "title": "Segue 2: The Least Massive Galaxy", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Boylan-Kolchin", "given_name": "Michael", "orcid": "0000-0002-9604-343X", "clpid": "Boylan-Kolchin-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Geha", "given_name": "Marla", "orcid": "0000-0002-7007-9725", "clpid": "Geha-M-C" }, { "family_name": "Bullock", "given_name": "James S.", "orcid": "0000-0003-4298-5082", "clpid": "Bullock-J-S" }, { "family_name": "Kaplinghat", "given_name": "Manoj", "clpid": "Kaplinghat-M" } ], "abstract": "Segue 2, discovered by Belokurov et al., is a galaxy with a luminosity of only 900 L_\u2609. We present Keck/DEIMOS spectroscopy of 25 members of Segue 2\u2014a threefold increase in spectroscopic sample size. The velocity dispersion is too small to be measured with our data. The upper limit with 90% (95%) confidence is \u03c3_v < 2.2 (2.6) km s^(\u20131), the most stringent limit for any galaxy. The corresponding limit on the mass within the three-dimensional half-light radius (46 pc) is M_(1/2) < 1.5 (2.1) \u00d7 10^5 M_\u2609. Segue 2 is the least massive galaxy known. We identify Segue 2 as a galaxy rather than a star cluster based on the wide dispersion in [Fe/H] (from \u20132.85 to \u20131.33) among the member stars. The stars' [\u03b1/Fe] ratios decline with increasing [Fe/H], indicating that Segue 2 retained Type Ia supernova ejecta despite its presently small mass and that star formation lasted for at least 100 Myr. The mean metallicity, \u3008[Fe/H]\u3009 = -2.22 \u00b1 0.13 (about the same as the Ursa Minor galaxy, 330 times more luminous than Segue 2), is higher than expected from the luminosity-metallicity relation defined by more luminous dwarf galaxy satellites of the Milky Way. Segue 2 may be the barest remnant of a tidally stripped, Ursa Minor-sized galaxy. If so, it is the best example of an ultra-faint dwarf galaxy that came to be ultra-faint through tidal stripping. Alternatively, Segue 2 could have been born in a very low mass dark matter subhalo (v_(max) < 10 km s^(\u20131)), below the atomic hydrogen cooling limit.", "doi": "10.1088/0004-637X/770/1/16", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2013-06-10", "series_number": "1", "volume": "770", "issue": "1", "pages": "Art. No. 16" }, { "id": "authors:m0eem-8k005", "collection": "authors", "collection_id": "m0eem-8k005", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20130226-090902254", "type": "article", "title": "Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. V. Evidence for a wide age distribution and a complex MDF", "author": [ { "family_name": "Bensby", "given_name": "T.", "clpid": "Bensby-T" }, { "family_name": "Yee", "given_name": "J. C.", "orcid": "0000-0001-9481-7123", "clpid": "Yee-Jennifer-C" }, { "family_name": "Feltzing", "given_name": "S.", "clpid": "Feltzing-S" }, { "family_name": "Johnson", "given_name": "J. A.", "orcid": "0000-0001-9808-7172", "clpid": "Johnson-J-A" }, { "family_name": "Gould", "given_name": "A.", "clpid": "Gould-A" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Asplund", "given_name": "M.", "clpid": "Asplund-M" }, { "family_name": "Mel\u00e9ndez", "given_name": "J.", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Lucatello", "given_name": "S.", "clpid": "Lucatello-S" }, { "family_name": "Han", "given_name": "C.", "clpid": "Han-C" }, { "family_name": "Thompson", "given_name": "I.", "clpid": "Thompson-I" }, { "family_name": "Gal-Yam", "given_name": "A.", "orcid": "0000-0002-3653-5598", "clpid": "Gal-Yam-A" }, { "family_name": "Udalski", "given_name": "A.", "orcid": "0000-0001-5207-5619", "clpid": "Udalski-A" }, { "family_name": "Bennett", "given_name": "D. P.", "orcid": "0000-0001-8043-8413", "clpid": "Bennett-D-P" }, { "family_name": "Bond", "given_name": "I. A.", "clpid": "Bond-I-A" }, { "family_name": "Kohei", "given_name": "W.", "clpid": "Kohei-W" }, { "family_name": "Sumi", "given_name": "T.", "clpid": "Sumi-Takahiro" }, { "family_name": "Suzuki", "given_name": "D.", "orcid": "0000-0002-5843-9433", "clpid": "Suzuki-Daisuke" }, { "family_name": "Suzuki", "given_name": "K.", "clpid": "Suzuki-K" }, { "family_name": "Takino", "given_name": "S.", "clpid": "Takino-S" }, { "family_name": "Tristram", "given_name": "P.", "clpid": "Tristram-P" }, { "family_name": "Yamai", "given_name": "N.", "clpid": "Yamai-N" }, { "family_name": "Yonehara", "given_name": "A.", "clpid": "Yonehara-A" } ], "abstract": "Based on high-resolution spectra obtained during gravitational microlensing events we present a detailed elemental abundance analysis of 32 dwarf and subgiant stars in the Galactic bulge. Combined with the sample of 26 stars from the previous papers in this series, we now have 58 microlensed bulge dwarfs and subgiants that have been homogeneously analysed. The main characteristics of the sample and the findings that can be drawn are: (i) the metallicity distribution (MDF) is wide and spans all metallicities between [Fe/H] = \u22121.9 to +0.6; (ii) the dip in the MDF around solar metallicity that was apparent in our previous analysis of a smaller sample (26 microlensed stars) is no longer evident; instead it has a complex structure and indications of multiple components are starting to emerge. A tentative interpretation is that there could be different stellar populations at interplay, each with a different scale height: the thin disk, the thick disk, and a bar population; (iii) the stars with [Fe/H] \u2272 \u22120.1 are old with ages between 10 and 12 Gyr; (iv) the metal-rich stars with [Fe/H] \u2273 \u22120.1 show a wide variety of ages, ranging from 2 to 12 Gyr with a distribution that has a dominant peak around 4\u22125 Gyr and a tail towards higher ages; (v) there are indications in the [\u03b1/Fe]\u2212[Fe/H] abundance trends that the \"knee\" occurs around [Fe/H] = \u22120.3 to \u22120.2, which is a slightly higher metallicity as compared to the \"knee\" for the local thick disk. This suggests that the chemical enrichment of the metal-poor bulge has been somewhat faster than what is observed for the local thick disk. The results from the microlensed bulge dwarf stars in combination with other findings in the literature, in particular the evidence that the bulge has cylindrical rotation, indicate that the Milky Way could be an almost pure disk galaxy. The bulge would then just be a conglomerate of the other Galactic stellar populations (thin disk, thick disk, halo, and ...?), residing together in the central parts of the Galaxy, influenced by the Galactic bar.", "doi": "10.1051/0004-6361/201220678", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2013-01", "volume": "549", "pages": "Art. No. A147" }, { "id": "authors:8a34w-kzn48", "collection": "authors", "collection_id": "8a34w-kzn48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190521-161105416", "type": "article", "title": "Extragalactic Globular Cluster Populations from High Resolution Integrated Light Spectra", "author": [ { "family_name": "Colucci", "given_name": "J. E.", "clpid": "Colucci-J-E" }, { "family_name": "Bernstein", "given_name": "R. A.", "clpid": "Bernstein-R-A" }, { "family_name": "McWilliam", "given_name": "A.", "clpid": "McWilliam-A" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present a comparison of high-resolution, integrated-light, detailed chemical abundances for Galactic and extragalactic globular clusters in both massive galaxies and dwarf galaxies. We include measurements of Fe, Ca, Si, Na, and Al for globular cluster samples in the Milky Way, M31, Large Magellanic Cloud, and NGC 5128. These and other recent results from our group on M31 and NGC 5128 are the first chemical abundances derived from discrete absorption features in old stars beyond the Milky Way and its nearest neighbors. These abundances can provide both galaxy enrichment histories and constraints on globular cluster formation and evolution.", "doi": "10.48550/arXiv.1302.6252", "issn": "0037-8720", "publisher": "Societ\u00e0 Astronomica Italiana", "publication": "Memorie della Societ\u00e0 Astronomica Italiana", "publication_date": "2013", "series_number": "1", "volume": "84", "issue": "1", "pages": "50-53" }, { "id": "authors:qp1rv-t8j12", "collection": "authors", "collection_id": "qp1rv-t8j12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121004-112928567", "type": "article", "title": "Detailed Abundances of Two Very Metal-Poor Stars in Dwarf Galaxies", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "The most metal-poor stars in dwarf spheroidal galaxies (dSphs) can show the nucleosynthetic patterns of one or a few supernovae (SNe). These SNe could have zero metallicity, making metal-poor dSph stars the closest surviving links to Population III stars. Metal-poor dSph stars also help to reveal the formation mechanism of the Milky Way (MW) halo. We present the detailed abundances from Keck/HIRES spectroscopy for two very metal-poor stars in two MW dSphs. One star, in the Sculptor dSph, has [Fe I/H] = -2.40. The other star, in the Ursa Minor dSph, has [Fe I/H] = -3.16. Both stars fall in the previously discovered low-metallicity, high-[\u03b1/Fe] plateau. Most abundance ratios of very metal-poor stars in these two dSphs are largely consistent with very metal-poor halo stars. However, the abundances of Na and some r-process elements lie at the lower end of the envelope defined by inner halo stars of similar metallicity. We propose that the metallicity dependence of SN yields is the cause. The earliest SNe in low-mass dSphs have less gas to pollute than the earliest SNe in massive halo progenitors. As a result, dSph stars at \u20133 < [Fe/H] < \u20132 sample SNe with [Fe/H] Lt \u20133, whereas halo stars in the same metallicity range sample SNe with [Fe/H] ~ \u20133. Consequently, enhancements in [Na/Fe] and [r/Fe] were deferred to higher metallicity in dSphs than in the progenitors of the inner halo.", "doi": "10.1088/0004-6256/144/6/168", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2012-12", "series_number": "6", "volume": "144", "issue": "6", "pages": "Art. No. 168" }, { "id": "authors:5y7xp-zy187", "collection": "authors", "collection_id": "5y7xp-zy187", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121219-112340754", "type": "article", "title": "The Bizarre Chemical Inventory of NGC 2419, An Extreme Outer Halo Globular Cluster", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" } ], "abstract": "We present new Keck/HIRES observations of six red giants in the globular cluster (GC) NGC 2419. Although the cluster is among the most distant and most luminous in the Milky Way, it was considered chemically ordinary until very recently. Our previous work showed that the near-infrared Ca II triplet line strength varied more than expected for a chemically homogeneous cluster, and that at least one star had unusual abundances of Mg and K. Here, we confirm that NGC 2419 harbors a population of stars, comprising about one-third of its mass, that is depleted in Mg by a factor of eight and enhanced in K by a factor of six with respect to the Mg-normal population. Although the majority, Mg-normal population appears to have a chemical abundance pattern indistinguishable from ordinary, inner-halo GCs, the Mg-poor population exhibits dispersions of several elements. The abundances of K and Sc are strongly anti-correlated with Mg, and some other elements (Si and Ca among others) are weakly anti-correlated with Mg. These abundance patterns suggest that the different populations of NGC 2419 sample the ejecta of diverse supernovae in addition to asymptotic giant branch ejecta. However, the abundances of Fe-peak elements except Sc show no star-to-star variation. We find no nucleosynthetic source that satisfactorily explains all of the abundance variations in this cluster. Because NGC 2419 appears like no other GC, we reiterate our previous suggestion that it is not a GC at all, but rather the core of an accreted dwarf galaxy.", "doi": "10.1088/0004-637X/760/1/86", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2012-11-20", "series_number": "1", "volume": "760", "issue": "1", "pages": "Art. No. 86" }, { "id": "authors:6wp3q-09890", "collection": "authors", "collection_id": "6wp3q-09890", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121022-131846051", "type": "book_section", "title": "The Chemical Evolution of Milky Way Satellite Galaxies from Keck/DEIMOS Multi-Element Abundance Measurements", "book_title": "Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Aoki", "given_name": "W.", "clpid": "Aoki-W" }, { "family_name": "Ishigaki", "given_name": "M.", "clpid": "Ishigaki-M" }, { "family_name": "Suda", "given_name": "T.", "clpid": "Suda-T" }, { "family_name": "Tsujimoto", "given_name": "T.", "clpid": "Tsujimoto-T" }, { "family_name": "Arimoto", "given_name": "N.", "clpid": "Arimoto-N" } ], "abstract": "A Keck/DEIMOS spectroscopic campaign of eight Milky Way (MW)\ndwarf spheroidal (dSph) satellite galaxies has generated spectral synthesis-based abundance measurements for nearly 3000 stars. The elements measured are Fe and the elements Mg, Si, Ca, and Ti. The dSph metallicity distributions show that the histories of the less luminous dSphs were marked by massive amounts of gas loss. The [/Fe] distributions indicate that the early star formation histories of most dSphs were very similar and that Type Ia supernova ejecta contributed to the abundances of all but the most metal-poor ([Fe/H] < \u22122.5) stars.", "isbn": "978-1-58381-798-8", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "2012-08-25", "pages": "329-330" }, { "id": "authors:16gdh-wz856", "collection": "authors", "collection_id": "16gdh-wz856", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20121022-131934431", "type": "book_section", "title": "Outliers in the 0Z Survey", "book_title": "Galactic Archaeology: Near-Field Cosmology and the Formation of the Milky Way", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Shectman", "given_name": "Stephen", "clpid": "Shectman-S" } ], "contributor": [ { "family_name": "Aoki", "given_name": "Wako", "clpid": "Aoki-Wako" }, { "family_name": "Ishigaki", "given_name": "M.", "clpid": "Ishigaki-M" }, { "family_name": "Suda", "given_name": "T.", "clpid": "Suda-T" }, { "family_name": "Tsujimoto", "given_name": "T.", "clpid": "Tsujimoto-T" }, { "family_name": "Arimoto", "given_name": "N.", "clpid": "Arimoto-Nobuo" } ], "abstract": "We have now completed detailed abundance analyses of more than 100 stars selected as candidate extremely metal-poor stars with [Fe/H] < \u20133.0 dex. Of these 18 are below \u20133.3 dex on the scale of the First Stars VLT project led by Cayrel, and 57 are below \u20133.0 dex on that scale. Ignoring enhancement of carbon which ranges up to very large values, and two C-rich stars with very high N as well, there are 0 to 3 high or low strong outliers for each abundance ratio tested from Mg to Ni. The outliers have been checked and they are real. Ignoring the outliers, the dispersions are in most cases approximately consistent with the uncertainties, except those for [Sr/Fe] and [Ba/Fe], which are much larger. Approximately 6% of the sample are strong outliers in one or more elements between Mg and Ni. This rises to \u223c15% if minor outliers for these elements and strong outliers for Sr and Ba are included. There are 6 stars with extremely low [Sr/Fe] and [Ba/Fe], including one which has lower [Ba/H] than Draco 119, the star found by Fulbright, Rich & Castro to have the lowest such ratio known previously. There is one extreme r-process star.", "doi": "10.48550/arXiv.1201.4190", "isbn": "978-1-58381-798-8", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "2012-08-25", "pages": "61-64" }, { "id": "authors:zzbg1-te088", "collection": "authors", "collection_id": "zzbg1-te088", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120618-134946055", "type": "article", "title": "Two Distant Halo Velocity Groups Discovered by the Palomar Transient Factory", "author": [ { "family_name": "Sesar", "given_name": "Branimir", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Levitan", "given_name": "David", "clpid": "Levitan-D" }, { "family_name": "Grillmair", "given_name": "Carl J.", "orcid": "0000-0003-4072-169X", "clpid": "Grillmair-C-J" }, { "family_name": "Juri\u0107", "given_name": "Mario", "clpid": "Juri\u0107-M" }, { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Laher", "given_name": "Russ R.", "orcid": "0000-0003-2451-5482", "clpid": "Laher-R-R" }, { "family_name": "Ofek", "given_name": "Eran O.", "orcid": "0000-0002-6786-8774", "clpid": "Ofek-E-O" }, { "family_name": "Surace", "given_name": "Jason A.", "orcid": "0000-0001-7291-0087", "clpid": "Surace-J-A" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Prince", "given_name": "Thomas A.", "orcid": "0000-0002-8850-3627", "clpid": "Prince-T-A" } ], "abstract": "We report the discovery of two new halo velocity groups (Cancer groups A and B) traced by 8 distant RR Lyrae stars and observed by the Palomar Transient Factory (PTF) survey at R.A.~129\u00b0, Dec~20\u00b0 (l~205\u00b0, b~32\u00b0). Located at 92 kpc from the Galactic center (86 kpc from the Sun), these are some of the most distant substructures in the Galactic halo known to date. Follow-up spectroscopic observations with the Palomar Observatory 5.1-m Hale telescope and W. M. Keck Observatory 10-m Keck I telescope indicate that the two groups are moving away from the Galaxy at v_(gsr) = 78.0+-5.6 km s^(-1) (Cancer group A) and v_(gsr) = 16.3+-7.1 km s^(-1) (Cancer group B). The groups have velocity dispersions of \u03c3_(v_)gsr))=12.4+-5.0 km s^(-1) and \u03c3 _(v_(gsr))=14.9+-6.2 km s^(-1), and are spatially extended (about several kpc) making it very unlikely that they are bound systems, and are more likely to be debris of tidally disrupted dwarf galaxies or globular clusters. Both groups are metal-poor (median metallicities of [Fe/H]^A = -1.6 dex and [Fe/H]^B =-2.1 dex), and have a somewhat uncertain (due to small sample size) metallicity dispersion of ~0.4 dex, suggesting dwarf galaxies as progenitors. Two additional RR Lyrae stars with velocities consistent with those of the Cancer groups have been observed ~25 \u00b0 east, suggesting possible extension of the groups in that direction.", "doi": "10.1088/0004-637X/755/2/134", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2012-08-20", "series_number": "2", "volume": "755", "issue": "2", "pages": "Art. No. 134" }, { "id": "authors:bak6h-hrk33", "collection": "authors", "collection_id": "bak6h-hrk33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120813-075720952", "type": "article", "title": "The Nature of Hypervelocity Stars and the Time between Their Formation and Ejection", "author": [ { "family_name": "Brown", "given_name": "Warren R.", "clpid": "Brown-W-R" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Geller", "given_name": "Margaret J.", "clpid": "Geller-M-J" }, { "family_name": "Kenyon", "given_name": "Scott J.", "orcid": "0000-0003-0214-609X", "clpid": "Kenyon-S-J" } ], "abstract": "We obtain Keck HIRES spectroscopy of HVS5, one of the fastest unbound stars in the Milky Way halo. We show that HVS5 is a 3.62 \u00b1 0.11 M_\u2609 main-sequence B star at a distance of 50 \u00b1 5 kpc. The difference between its age and its flight time from the Galactic center is 105 \u00b1 18 (stat) \u00b130 (sys) Myr; flight times from locations elsewhere in the Galactic disk are similar. This 10^8 yr \"arrival time\" between formation and ejection is difficult to reconcile with any ejection scenario involving massive stars that live for only 10^7 yr. For comparison, we derive arrival times of 10^7 yr for two unbound runaway B stars, consistent with their disk origin where ejection results from a supernova in a binary system or dynamical interactions between massive stars in a dense star cluster. For HVS5, ejection during the first 10^7 yr of its lifetime is ruled out at the 3\u03c3 level. Together with the 10^8 yr arrival times inferred for three other well-studied hypervelocity stars (HVSs), these results are consistent with a Galactic center origin for the HVSs. If the HVSs were indeed ejected by the central black hole, then the Galactic center was forming stars \u2243200 Myr ago, and the progenitors of the HVSs took \u2243100 Myr to enter the black hole's loss cone.", "doi": "10.1088/2041-8205/754/1/L2", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2012-07-20", "series_number": "1", "volume": "754", "issue": "1", "pages": "Art. No. L2" }, { "id": "authors:kmgmc-ay740", "collection": "authors", "collection_id": "kmgmc-ay740", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120817-095123257", "type": "article", "title": "The complex case of V445 Lyr observed with Kepler: two Blazhko modulations, a non-radial mode, possible triple mode RR Lyrae pulsation, and more", "author": [ { "family_name": "Guggenberger", "given_name": "E.", "clpid": "Guggenberger-E" }, { "family_name": "Kolenberg", "given_name": "K.", "clpid": "Kolenberg-K" }, { "family_name": "Nemec", "given_name": "J. M.", "clpid": "Nemec-J-M" }, { "family_name": "Smolec", "given_name": "R.", "orcid": "0000-0001-7217-4884", "clpid": "Smolec-R" }, { "family_name": "Benk\u0151", "given_name": "J. M.", "clpid": "Benk\u0151-J-M" }, { "family_name": "Ngeow", "given_name": "C.-C.", "orcid": "0000-0001-8771-7554", "clpid": "Ngeow-Chow-Choong" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Sesar", "given_name": "B.", "orcid": "0000-0002-0834-3978", "clpid": "Sesar-B" }, { "family_name": "Szab\u03cc", "given_name": "R.", "clpid": "Szab\u03cc-R" }, { "family_name": "Catelan", "given_name": "M.", "orcid": "0000-0001-6003-8877", "clpid": "Catelan-M" }, { "family_name": "Moskalik", "given_name": "P.", "clpid": "Moskalik-P" }, { "family_name": "Kinemuchi", "given_name": "K.", "clpid": "Kinemuchi-K" }, { "family_name": "Seader", "given_name": "S. E.", "clpid": "Seader-S-E" }, { "family_name": "Smith", "given_name": "J. C.", "clpid": "Smith-J-C" }, { "family_name": "Tenenbaum", "given_name": "P.", "clpid": "Tenenbaum-P" }, { "family_name": "Kjeldsen", "given_name": "H.", "clpid": "Kjeldsen-H" } ], "abstract": "Rapid and strong changes in the Blazhko modulation of RR Lyrae stars, as have recently been detected in high-precision satellite data, have become a crucial topic in finding an explanation of the long-standing mystery of the Blazhko effect. We present here an analysis of the most extreme case detected so far, the RRab star V445 Lyr (KIC 6186029) which was observed with the Kepler space mission. V445 Lyr shows very strong cycle-to-cycle changes in its Blazhko modulation, which are caused by both a secondary long-term modulation period and irregular variations. In addition to the complex Blazhko modulation, V445 Lyr also shows a rich spectrum of additional peaks in the frequency range between the fundamental pulsation and the first harmonic. Among those peaks, the second radial overtone could be identified, which, combined with a metallicity estimate of [Fe/H] =\u22122.0 dex from spectroscopy, allowed us to constrain the mass (0.55\u20130.65 M_\u2299) and luminosity (40\u201350 L_\u2299) of V445 Lyr through theoretical Petersen diagrams. A non-radial mode and possibly the first overtone are also excited. Furthermore, V445 Lyr shows signs of the period-doubling phenomenon and a long-term period change. A detailed Fourier analysis along with a study of the O \u2212 C variation of V445 Lyr is presented, and the origin of the additional peaks and possible causes of the changes in the Blazhko modulation are discussed. The results are then put into context with those of the only other star with a variable Blazhko effect for which a long enough set of high-precision continuous satellite data has been published so far, the CoRoT star 105288363.", "doi": "10.1111/j.1365-2966.2012.21244.x", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2012-07", "series_number": "1", "volume": "424", "issue": "1", "pages": "649-665" }, { "id": "authors:ht6fh-43c28", "collection": "authors", "collection_id": "ht6fh-43c28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190521-153209832", "type": "article", "title": "The remarkable solar twin HIP\u00a056948: a prime target in the quest for other Earths", "author": [ { "family_name": "Mel\u00e9ndez", "given_name": "J.", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Bergemann", "given_name": "M.", "clpid": "Bergemann-M" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Endl", "given_name": "M.", "orcid": "0000-0002-7714-6310", "clpid": "Endl-M" }, { "family_name": "Karakas", "given_name": "A. I.", "orcid": "0000-0002-3625-6951", "clpid": "Karakas-A-I" }, { "family_name": "Ram\u00edrez", "given_name": "I.", "clpid": "Ram\u00edrez-I" }, { "family_name": "Cochran", "given_name": "W. D.", "orcid": "0000-0001-9662-3496", "clpid": "Cochran-W-D" }, { "family_name": "Yong", "given_name": "D.", "clpid": "Yong-D" }, { "family_name": "MacQueen", "given_name": "P. J.", "clpid": "MacQueen-P-J" }, { "family_name": "Kobayashi", "given_name": "C.", "clpid": "Kobayashi-C" }, { "family_name": "Asplund", "given_name": "M.", "clpid": "Asplund-M" } ], "abstract": "Context. The Sun shows abundance anomalies relative to most solar twins. If the abundance peculiarities are due to the formation of inner rocky planets, that would mean that only a small fraction of solar type stars may host terrestrial planets. \n\nAims. In this work we study HIP 56948, the best solar twin known to date, to determine with an unparalleled precision how similar it is to the Sun in its physical properties, chemical composition and planet architecture. We explore whether the abundances anomalies may be due to pollution from stellar ejecta or to terrestrial planet formation.\nMethods. We perform a differential abundance analysis (both in LTE and NLTE) using high resolution (R ~ 100 000) high S/N (600\u2013650) Keck HIRES spectra of the Sun (as reflected from the asteroid Ceres) and HIP 56948. We use precise radial velocity data from the McDonald and Keck observatories to search for planets around this star. \n\nResults. We achieve a precision of \u03c3 \u2272 0.003 dex for several elements. Including errors in stellar parameters the total uncertainty is as low as \u03c3 \u2243 0.005 dex (1%), which is unprecedented in elemental abundance studies. The similarities between HIP 56948 and the Sun are astonishing. HIP 56948 is only 17 \u00b1 7 K hotter than the Sun, and log g, [Fe/H] and microturbulence velocity are only + 0.02 \u00b1 0.02 dex, +0.02 \u00b1 0.01 dex and +0.01 \u00b1 0.01 km s^(-1) higher than solar, respectively. Our precise stellar parameters and a differential isochrone analysis shows that HIP 56948 has a mass of 1.02 \u00b1 0.02 M\u2299 and that it is ~1 Gyr younger than the Sun, as constrained by isochrones, chromospheric activity, Li and rotation. Both stars show a chemical abundance pattern that differs from most solar twins, but the refractory elements (those with condensation temperature T_(cond) \u2273 1000 K) are slightly (~0.01 dex) more depleted in the Sun than in HIP 56948. The trend with T_(cond) in differential abundances (twins \u2212 HIP 56948) can be reproduced very well by adding ~3 M\u2295 of a mix of Earth and meteoritic material, to the convection zone of HIP 56948. The element-to-element scatter of the Earth/meteoritic mix for the case of hypothetical rocky planets around HIP 56948 is only 0.0047 dex. From our radial velocity monitoring we find no indications of giant planets interior to or within the habitable zone of HIP 56948. \n\nConclusions. We conclude that HIP 56948 is an excellent candidate to host a planetary system like our own, including the possible presence of inner terrestrial planets. Its striking similarity to the Sun and its mature age makes HIP 56948 a prime target in the quest for other Earths and SETI endeavors.", "doi": "10.1051/0004-6361/201117222", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2012-07", "volume": "543", "pages": "Art. No. A29" }, { "id": "authors:z6hq3-dhy41", "collection": "authors", "collection_id": "z6hq3-dhy41", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120919-115003942", "type": "article", "title": "The remarkable solar twin HIP 56948: a prime target in the quest for other Earths", "author": [ { "family_name": "Mel\u00e9ndez", "given_name": "J.", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Bergemann", "given_name": "M.", "clpid": "Bergemann-M" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Endl", "given_name": "M.", "orcid": "0000-0002-7714-6310", "clpid": "Endl-M" }, { "family_name": "Karakas", "given_name": "A. I.", "orcid": "0000-0002-3625-6951", "clpid": "Karakas-A-I" }, { "family_name": "Ram\u00edrez", "given_name": "I.", "clpid": "Ram\u00edrez-I" }, { "family_name": "Cochran", "given_name": "W. D.", "orcid": "0000-0001-9662-3496", "clpid": "Cochran-W-D" }, { "family_name": "Yong", "given_name": "D.", "clpid": "Yong-D" }, { "family_name": "MacQueen", "given_name": "P. J.", "clpid": "MacQueen-P-J" }, { "family_name": "Kobayashi", "given_name": "C.", "clpid": "Kobayashi-C" }, { "family_name": "Asplund", "given_name": "M.", "clpid": "Asplund-M" } ], "abstract": "Context. The Sun shows abundance anomalies relative to most solar twins. If the abundance peculiarities are due to the formation of inner rocky planets, that would mean that only a small fraction of solar type stars may host terrestrial planets.\nAims. In this work we study HIP 56948, the best solar twin known to date, to determine with an unparalleled precision how similar it is to the Sun in its physical properties, chemical composition and planet architecture. We explore whether the abundances anomalies may be due to pollution from stellar ejecta or to terrestrial planet formation.\nMethods. We perform a differential abundance analysis (both in LTE and NLTE) using high resolution (R ~ 100 000) high S/N (600\u2013650) Keck HIRES spectra of the Sun (as reflected from the asteroid Ceres) and HIP 56948. We use precise radial velocity data from the McDonald and Keck observatories to search for planets around this star.\nResults. We achieve a precision of \u03c3 \u2272 0.003 dex for several elements. Including errors in stellar parameters the total uncertainty is as low as \u03c3 \u2243 0.005 dex (1%), which is unprecedented in elemental abundance studies. The similarities between HIP 56948 and the Sun are astonishing. HIP 56948 is only 17 \u00b1 7 K hotter than the Sun, and log g, [Fe/H] and microturbulence velocity are only + 0.02 \u00b1 0.02 dex, +0.02 \u00b1 0.01 dex and +0.01 \u00b1 0.01 km s^(-1) higher than solar, respectively. Our precise stellar parameters and a differential isochrone analysis shows that HIP 56948 has a mass of 1.02 \u00b1 0.02 M_\u2299 and that it is ~1 Gyr younger than the Sun, as constrained by isochrones, chromospheric activity, Li and rotation. Both stars show a chemical abundance pattern that differs from most solar twins, but the refractory elements (those with condensation temperature T_(cond) \u2273 1000 K) are slightly (~0.01 dex) more depleted in the Sun than in HIP 56948. The trend with T_(cond) in differential abundances (twins \u2212 HIP 56948) can be reproduced very well by adding ~3 M_\u2295 of a mix of Earth and meteoritic material, to the convection zone of HIP 56948. The element-to-element scatter of the Earth/meteoritic mix for the case of hypothetical rocky planets around HIP 56948 is only 0.0047 dex. From our radial velocity monitoring we find no indications of giant planets interior to or within the habitable zone of HIP 56948.\nConclusions. We conclude that HIP 56948 is an excellent candidate to host a planetary system like our own, including the possible presence of inner terrestrial planets. Its striking similarity to the Sun and its mature age makes HIP 56948 a prime target in the quest for other Earths and SETI endeavors.", "doi": "10.1051/0004-6361/201117222", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2012-07", "volume": "543", "pages": "Art. No. A29" }, { "id": "authors:ht6vn-x5a60", "collection": "authors", "collection_id": "ht6vn-x5a60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20120409-082635030", "type": "article", "title": "The Dynamics and Metallicity Distribution of the Distant Dwarf Galaxy VV124", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Bellazzini", "given_name": "Michele", "orcid": "0000-0001-8200-810X", "clpid": "Bellazzini-M" } ], "abstract": "VV124 (UGC 4879) is an isolated, dwarf irregular/dwarf spheroidal (dIrr/dSph) transition-type\ngalaxy at a distance of 1.36 Mpc. Previous low-resolution spectroscopy yielded inconsistent radial\nvelocities for different components of the galaxy, and photometry hinted at the presence of a stellar\ndisk. In order to quantify the stellar dynamics, we observed individual red giants in VV124 with the Keck/DEIMOS spectrograph. We validated members based on their positions in the color-magnitude\ndiagram, radial velocities, and spectral features. Our sample contains 67 members. The average\nradial velocity is = \u221229.1 \u00b1 1.3 km s^(\u22121), in agreement with the previous radio measurements\nof H I gas. The velocity distribution is Gaussian, indicating that VV124 is supported primarily by\nvelocity dispersion inside a radius of 1.5 kpc. Outside that radius, our measurements provide only an\nupper limit of 8.6 km s^(\u22121) on any rotation in the photometric disk-like feature. The velocity dispersion\nis \u03c3_v = 9.4\u00b1 1.0 km s^(\u22121), from which we inferred a mass of M_(1/2) = (2.1 \u00b1 0.2)\u00d7 10^7 M_\u2299 and a mass-to-\nlight ratio of (M/L_V)_(1/2) = 5.2 \u00b1 1.1 M_\u2299/L_\u2299, both measured within the half-light radius. Thus,\nVV124 contains dark matter. We also measured the metallicity distribution from neutral iron lines.\nThe average metallicity, <[Fe/H]> = \u22121.14 \u00b1 0.06, is consistent with the mass-metallicity relation\ndefined by dwarf spheroidal galaxies. The dynamics and metallicity distribution of VV124 appear\nsimilar to dSphs of similar stellar mass.", "doi": "10.1088/0004-637X/751/1/46", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2012-05-20", "series_number": "1", "volume": "751", "issue": "1", "pages": "Art. No. 46" }, { "id": "authors:jvh4k-r8x55", "collection": "authors", "collection_id": "jvh4k-r8x55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190521-161528584", "type": "monograph", "title": "Signatures of an intermediate-age metal-rich bulge population", "author": [ { "family_name": "Bensby", "given_name": "T.", "clpid": "Bensby-T" }, { "family_name": "Feltzing", "given_name": "S.", "clpid": "Feltzing-S" }, { "family_name": "Gould", "given_name": "A.", "clpid": "Gould-A" }, { "family_name": "Johnson", "given_name": "J. A.", "orcid": "0000-0001-9808-7172", "clpid": "Johnson-J-A" }, { "family_name": "Asplund", "given_name": "M.", "clpid": "Asplund-M" }, { "family_name": "Ad\u00e9n", "given_name": "D.", "clpid": "Ad\u00e9n-D" }, { "family_name": "Mel\u00e9ndez", "given_name": "J.", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Thompson", "given_name": "I.", "clpid": "Thompson-I" }, { "family_name": "Lucatello", "given_name": "S.", "clpid": "Lucatello-S" }, { "family_name": "Gal-Yam", "given_name": "A.", "orcid": "0000-0002-3653-5598", "clpid": "Gal-Yam-A" } ], "abstract": "We have determined detailed elemental abundances and stellar ages for a sample of now 38 microlensed dwarf and subgiant stars in the Galactic bulge. Stars with sub-solar metallicities are all old and have enhanced alpha-element abundances -- very similar to what is seen for local thick disk stars. The metal-rich stars on the other hand show a wide variety of stellar ages, ranging from 3-4 Gyr to 12 Gyr, and an average around 7-8 Gyr. The existence of young and metal-rich stars are in conflict with recent photometric studies of the bulge which claim that the bulge only contains old stars.", "doi": "10.48550/arXiv.1201.2013", "publisher": "arXiv", "publication_date": "2012-01-10" }, { "id": "authors:tdwy8-saa24", "collection": "authors", "collection_id": "tdwy8-saa24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111209-094859011", "type": "article", "title": "SN 2011dh: Discovery of a Type IIb Supernova from a Compact Progenitor in the Nearby Galaxy M51", "author": [ { "family_name": "Arcavi", "given_name": "Iair", "orcid": "0000-0001-7090-4898", "clpid": "Arcavi-I" }, { "family_name": "Kasliwal", "given_name": "Mansi M.", "orcid": "0000-0002-5619-4938", "clpid": "Kasliwal-M-M" }, { "family_name": "Quimby", "given_name": "Robert M.", "orcid": "0000-0001-9171-5236", "clpid": "Quimby-R-M" }, { "family_name": "Ofek", "given_name": "Eran O.", "orcid": "0000-0002-6786-8774", "clpid": "Ofek-E-O" }, { "family_name": "Horesh", "given_name": "Assaf", "orcid": "0000-0002-5936-1156", "clpid": "Horesh-A" }, { "family_name": "Kulkarni", "given_name": "Shrinivas R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Fulton", "given_name": "Benjamin J.", "orcid": "0000-0003-3504-5316", "clpid": "Fulton-B-J" } ], "abstract": "On 2011 May 31 UT a supernova (SN) exploded in the nearby galaxy M51 (the Whirlpool Galaxy). We discovered this event using small telescopes equipped with CCD cameras and also detected it with the Palomar Transient Factory survey, rapidly confirming it to be a Type II SN. Here, we present multi-color ultraviolet through infrared photometry which is used to calculate the bolometric luminosity and a series of spectra. Our early-time observations indicate that SN 2011dh resulted from the explosion of a relatively compact progenitor star. Rapid shock-breakout cooling leads to relatively low temperatures in early-time spectra, compared to explosions of red supergiant stars, as well as a rapid early light curve decline. Optical spectra of SN 2011dh are dominated by H lines out to day 10 after explosion, after which He I lines develop. This SN is likely a member of the cIIb (compact IIb) class, with progenitor radius larger than that of SN 2008ax and smaller than the eIIb (extended IIb) SN 1993J progenitor. Our data imply that the object identified in pre-explosion Hubble Space Telescope images at the SN location is possibly a companion to the progenitor or a blended source, and not the progenitor star itself, as its radius (~10^(13) cm) would be highly inconsistent with constraints from our post-explosion spectra.", "doi": "10.1088/2041-8205/742/2/L18", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2011-12-01", "series_number": "2", "volume": "742", "issue": "2", "pages": "L18" }, { "id": "authors:k0z2e-qtd26", "collection": "authors", "collection_id": "k0z2e-qtd26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111206-090232829", "type": "article", "title": "The Peculiar Chemical Inventory of NGC 2419: an Extreme Outer Halo \"Globular Cluster\"", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Huang", "given_name": "Wenjin", "clpid": "Huang-Wenjin" }, { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" } ], "abstract": "NGC 2419 is a massive outer halo Galactic globular cluster (GC) whose stars have previously been shown to have\nsomewhat peculiar abundance patterns. We have observed seven luminous giants that are members of NGC 2419\nwith Keck/HIRES at reasonable signal-to-noise ratio. One of these giants is very peculiar, with an extremely low\n[Mg/Fe] and high [K/Fe] but normal abundances of most other elements. The abundance pattern does not match\nthe nucleosynthetic yields of any supernova model. The other six stars show abundance ratios typical of inner halo\nGalactic GCs, represented here by a sample of giants in the nearby GC M30. Although our measurements show\nthat NGC 2419 is unusual in some respects, its bulk properties do not provide compelling evidence for a difference between inner and outer halo GCs.", "doi": "10.1088/0004-637X/740/2/60", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2011-10-20", "series_number": "2", "volume": "740", "issue": "2", "pages": "Art. No. 60" }, { "id": "authors:0dhyd-v9g94", "collection": "authors", "collection_id": "0dhyd-v9g94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111206-094432994", "type": "article", "title": "No Heavy-Element Dispersion in the Globular Cluster M92", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Although there have been recent claims that there is a large dispersion in the abundances of the heavy neutron capture elements in the old Galactic globular cluster M92, we show that the measured dispersion for the absolute abundances of four of the rare earth elements within a sample of 12 luminous red giants in M92 (\u22640.07 dex) does not exceed the relevant sources of uncertainty. As expected from previous studies, the heavy elements show the signature of the r-process. Their abundance ratios are essentially identical to those of M30, another nearby globular cluster of similar metallicity.", "doi": "10.1088/2041-8205/740/2/L38", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2011-10-20", "series_number": "2", "volume": "740", "issue": "2", "pages": "Art. No. L38" }, { "id": "authors:p5chc-fet92", "collection": "authors", "collection_id": "p5chc-fet92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20111024-091002541", "type": "article", "title": "Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. IV. Two bulge populations", "author": [ { "family_name": "Bensby", "given_name": "T.", "clpid": "Bensby-T" }, { "family_name": "Ad\u00e9n", "given_name": "D.", "clpid": "Ad\u00e9n-D" }, { "family_name": "Mel\u00e9ndez", "given_name": "J.", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Gould", "given_name": "A.", "clpid": "Gould-A" }, { "family_name": "Feltzing", "given_name": "S.", "clpid": "Feltzing-S" }, { "family_name": "Asplund", "given_name": "M.", "clpid": "Asplund-M" }, { "family_name": "Johnson", "given_name": "J. A.", "orcid": "0000-0001-9808-7172", "clpid": "Johnson-J-A" }, { "family_name": "Lucatello", "given_name": "S.", "clpid": "Lucatello-S" }, { "family_name": "Yee", "given_name": "J. C.", "orcid": "0000-0001-9481-7123", "clpid": "Yee-Jennifer-C" }, { "family_name": "Ram\u00edrez", "given_name": "I.", "clpid": "Ram\u00edrez-I" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Thompson", "given_name": "I.", "clpid": "Thompson-I-B" }, { "family_name": "Bond", "given_name": "I. A.", "clpid": "Bond-I-A" }, { "family_name": "Gal-Yam", "given_name": "A.", "orcid": "0000-0002-3653-5598", "clpid": "Gal-Yam-A" }, { "family_name": "Han", "given_name": "C.", "clpid": "Han-C" }, { "family_name": "Sumi", "given_name": "T.", "clpid": "Sumi-Takahiro" }, { "family_name": "Suzuki", "given_name": "D.", "orcid": "0000-0002-5843-9433", "clpid": "Suzuki-Daisuke" }, { "family_name": "Wada", "given_name": "K.", "clpid": "Wada-K" }, { "family_name": "Miyake", "given_name": "N.", "clpid": "Miyake-N" }, { "family_name": "Furusawa", "given_name": "K.", "clpid": "Furusawa-K" }, { "family_name": "Ohmori", "given_name": "K.", "clpid": "Ohmori-K" }, { "family_name": "Saito", "given_name": "To.", "clpid": "Saito-To" }, { "family_name": "Tristram", "given_name": "P.", "clpid": "Tristram-P-J" }, { "family_name": "Bennett", "given_name": "D.", "orcid": "0000-0001-8043-8413", "clpid": "Bennett-D-P" } ], "abstract": "Based on high-resolution (R \u2248 42 000 to 48 000) and high signal-to-noise (S/N \u2248 50 to 150) spectra obtained with UVES/VLT, we present detailed elemental abundances (O, Na, Mg, Al, Si, Ca, Ti, Cr, Fe, Ni, Zn, Y, and Ba) and stellar ages for 12 new microlensed dwarf and subgiant stars in the Galactic bulge. Including previous microlensing events, the sample of homogeneously analysed bulge dwarfs has now grown to 26. The analysis is based on equivalent width measurements and standard 1-D LTE MARCS model stellar atmospheres. We also present NLTE Li abundances based on line synthesis of the ^7Li line at 670.8\u2009nm. The results from the 26 microlensed dwarf and subgiant stars show that the bulge metallicity distribution (MDF) is double-peaked; one peak at [Fe/H] \u2248 \u22120.6 and one at [Fe/H] \u2248 + 0.3, and with a dearth of stars around solar metallicity. This is in contrast to the MDF derived from red giants in Baade's window, which peaks at this exact value. A simple significance test shows that it is extremely unlikely to have such a gap in the microlensed dwarf star MDF if the dwarf stars are drawn from the giant star MDF. To resolve this issue we discuss several possibilities, but we can not settle on a conclusive solution for the observed differences. We further find that the metal-poor bulge dwarf stars arepredominantly old with ages greater than 10\u2009Gyr, while the metal-rich bulge dwarf stars show a wide range of ages. The metal-poor bulge sample is very similar to the Galactic thick disk in terms of average metallicity, elemental abundance trends, and stellar ages. Speculatively, the metal-rich bulge population might be the manifestation of the inner thin disk. If so, the two bulge populations could support the recent findings, based on kinematics, that there are no signatures of a classical bulge and that the Milky Way is a pure-disk galaxy. Also, recent claims of a flat IMF in the bulge based on the MDF of giant stars may have to be revised based on the MDF and abundance trends probed by our microlensed dwarf stars.", "doi": "10.1051/0004-6361/201117059", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2011-09", "volume": "533", "pages": "Art. No. A134" }, { "id": "authors:5gz40-csp09", "collection": "authors", "collection_id": "5gz40-csp09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190521-161942082", "type": "monograph", "title": "A Status Report on the 0Z Project", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Shectman", "given_name": "Stephen", "clpid": "Shectman-S-A" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" } ], "abstract": "We present an update on the status of the 0Z Survey, an effort to datamine the Hamburg/ESO Survey to find and study in detail a large sample of extremely metal-poor Galactic halo field stars with [Fe/H] < -3 dex. After searching 1,565 moderate resolution spectra of candidates selected from the HES, we have acquired high resolution spectra of 103 of the most metal-poor of them. Detailed abundance analyses have been performed for all these stars. This has resulted in the discovery of 18 new stars below [Fe/H] -3.5 dex and 57 below -3.0 dex. Some results are presented regarding our search for outliers in chemical abundances of particular species among the sample of 103 stars. Ignoring C and N, about 15% of the sample are \"abnormal\" in some way. Our plans to complete this project and write the final set of papers are described.", "doi": "10.48550/arXiv.1105.1126", "publisher": "arXiv", "publication_date": "2011-05-05" }, { "id": "authors:zy6d9-qmj14", "collection": "authors", "collection_id": "zy6d9-qmj14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110310-100115284", "type": "article", "title": "Multi-element Abundance Measurements from Medium-resolution Spectra. III. Metallicity Distributions of Milky Way Dwarf Satellite Galaxies", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Lanfranchi", "given_name": "Gustavo A.", "clpid": "Lanfranchi-G-A" }, { "family_name": "Simon", "given_name": "Joshua D.", "clpid": "Simon-J-D" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Guhathakurta", "given_name": "Puragra", "orcid": "0000-0001-8867-4234", "clpid": "Guhathakurta-P" } ], "abstract": "We present metallicity distribution functions (MDFs) for the central regions of eight dwarf satellite galaxies of\nthe Milky Way: Fornax, Leo I and II, Sculptor, Sextans, Draco, Canes Venatici I, and Ursa Minor. We use the\npublished catalog of abundance measurements from the previous paper in this series. The measurements are based\non spectral synthesis of iron absorption lines. For each MDF, we determine maximum likelihood fits for Leaky Box,\nPre-Enriched, and Extra Gas (wherein the gas supply available for star formation increases before it decreases to zero) analytic models of chemical evolution. Although the models are too simplistic to describe any MDF in detail,\na Leaky Box starting from zero metallicity gas fits none of the galaxies except Canes Venatici I well. The MDFs of\nsome galaxies, particularly the more luminous ones, strongly prefer the Extra Gas Model to the other models. Only for Canes Venatici I does the Pre-Enriched Model fit significantly better than the Extra Gas Model. The best-fit\neffective yields of the less luminous half of our galaxy sample do not exceed 0.02Z_\u2299, indicating that gas outflow\nis important in the chemical evolution of the less luminous galaxies. We surmise that the ratio of the importance\nof gas infall to gas outflow increases with galaxy luminosity. Strong correlations of average [Fe/H] and metallicity spread with luminosity support this hypothesis.", "doi": "10.1088/0004-637X/727/2/78", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2011-02-01", "series_number": "2", "volume": "727", "issue": "2", "pages": "Art. No. 78" }, { "id": "authors:ys5dk-bts29", "collection": "authors", "collection_id": "ys5dk-bts29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110310-100115617", "type": "article", "title": "Multi-element Abundance Measurements from Medium-resolution Spectra. IV. Alpha Element Distributions in Milky Way Satellite Galaxies", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Smith", "given_name": "Graeme H.", "clpid": "Smith-G-H" }, { "family_name": "Majewski", "given_name": "Steven R.", "orcid": "0000-0003-2025-3147", "clpid": "Majewski-S-R" }, { "family_name": "Sohn", "given_name": "Sangmo Tony", "clpid": "Sohn-Sangmo-Tony" }, { "family_name": "Guhathakurta", "given_name": "Puragra", "orcid": "0000-0001-8867-4234", "clpid": "Guhathakurta-P" } ], "abstract": "We derive the star formation histories of eight dwarf spheroidal (dSph) Milky Way satellite galaxies from their\nalpha element abundance patterns. Nearly 3000 stars from our previously published catalog comprise our data\nset. The average [\u03b1/Fe] ratios for all dSphs follow roughly the same path with increasing [Fe/H]. We do not\nobserve the predicted knees in the [\u03b1/Fe] versus [Fe/H] diagram, corresponding to the metallicity at which Type Ia\nsupernovae begin to explode. Instead, we find that Type Ia supernova ejecta contribute to the abundances of all but\nthe most metal-poor ([Fe/H] < \u22122.5) stars.We have also developed a chemical evolution model that tracks the star\nformation rate, Types II and Ia supernova explosions, and supernova feedback. Without metal enhancement in the\nsupernova blowout, massive amounts of gas loss define the history of all dSphs except Fornax, the most luminous in\nour sample. All six of the best-fit model parameters correlate with dSph luminosity but not with velocity dispersion, half-light radius, or Galactocentric distance.", "doi": "10.1088/0004-637X/727/2/79", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2011-02-01", "series_number": "2", "volume": "727", "issue": "2", "pages": "Art. No. 79" }, { "id": "authors:gqc69-dfg55", "collection": "authors", "collection_id": "gqc69-dfg55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101223-095343420", "type": "article", "title": "NGC 2419-Another Remnant of Accretion by the Milky Way", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Simon", "given_name": "Joshua D.", "clpid": "Simon-J-D" }, { "family_name": "Geha", "given_name": "Marla", "orcid": "0000-0002-7007-9725", "clpid": "Geha-M-C" } ], "abstract": "We isolate a sample of 43 upper red giant branch stars in the extreme outer halo Galactic globular cluster (GC) NGC 2419 from two Keck/DEIMOS slitmasks. The probability that there is more than one contaminating halo field star in this sample is extremely low. Analysis of moderate-resolution spectra of these cluster members, as well as of our Keck/HIRES high-resolution spectra of a subsample of them, demonstrates that there is a small but real spread in Ca abundance of ~0.2 dex within this massive metal-poor GC. This provides additional support to earlier suggestions that NGC 2419 is the remnant of a dwarf galaxy accreted long ago by the Milky Way.", "doi": "10.1088/0004-637X/725/1/288", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2010-12-10", "series_number": "1", "volume": "725", "issue": "1", "pages": "288-295" }, { "id": "authors:yjs02-k1a46", "collection": "authors", "collection_id": "yjs02-k1a46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110310-100114131", "type": "article", "title": "Multi-element Abundance Measurements from Medium-resolution Spectra. II. Catalog of Stars in Milky Way Dwarf Satellite Galaxies", "author": [ { "family_name": "Kirby", "given_name": "Evan N.", "orcid": "0000-0001-6196-5162", "clpid": "Kirby-E-N" }, { "family_name": "Guhathakurta", "given_name": "Puragra", "orcid": "0000-0001-8867-4234", "clpid": "Guhathakurta-P" }, { "family_name": "Simon", "given_name": "Joshua D.", "clpid": "Simon-J-D" }, { "family_name": "Geha", "given_name": "Marla C.", "orcid": "0000-0002-7007-9725", "clpid": "Geha-M-C" }, { "family_name": "Rockosi", "given_name": "Constance M.", "clpid": "Rockosi-C-M" }, { "family_name": "Sneden", "given_name": "Christopher", "orcid": "0000-0002-3456-5929", "clpid": "Sneden-C" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Sohn", "given_name": "Sangmo Tony", "clpid": "Sohn-Sangmo-Tony" }, { "family_name": "Majewski", "given_name": "Steven R.", "orcid": "0000-0003-2025-3147", "clpid": "Majewski-S-R" }, { "family_name": "Siegel", "given_name": "Michael", "clpid": "Siegel-M" } ], "abstract": "We present a catalog of Fe, Mg, Si, Ca, and Ti abundances for 2961 stars in eight dwarf satellite galaxies of the Milky Way (MW): Sculptor, Fornax, Leo I, Sextans, Leo II, Canes Venatici I, Ursa Minor, and Draco. For the purposes of\nvalidating our measurements, we also observed 445 red giants in MW globular clusters and 21 field red giants in the MW halo. Themeasurements are based on Keck/DEIMOS medium-resolution spectroscopy (MRS) combined with\nspectral synthesis. We estimate uncertainties in [Fe/H] by quantifying the dispersion of [Fe/H] measurements in a\nsample of stars inmonometallic globular clusters (GCs).We estimate uncertainties in Mg, Si, Ca, and Ti abundances\nby comparing to high-resolution spectroscopic abundances of the same stars. For this purpose, a sample of 132\nstars with published high-resolution spectroscopy in GCs, the MW halo field, and dwarf galaxies has been observed\nwith MRS. The standard deviations of the differences in [Fe/H] and ([\u03b1/Fe]) (the average of [Mg/Fe], [Si/Fe],\n[Ca/Fe], and [Ti/Fe]) between the two samples is 0.15 and 0.16, respectively. This catalog represents the largest\nsample of multi-element abundances in dwarf galaxies to date. The next papers in this series draw conclusions on\nthe chemical evolution, gas dynamics, and star formation histories from the catalog presented here. The wide range\nof dwarf galaxy luminosity reveals the dependence of dwarf galaxy chemical evolution on galaxy stellar mass.", "doi": "10.1088/0067-0049/191/2/352", "issn": "0067-0049", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Supplement Series", "publication_date": "2010-12", "series_number": "2", "volume": "191", "issue": "2", "pages": "352-375" }, { "id": "authors:dbd4z-7jc63", "collection": "authors", "collection_id": "dbd4z-7jc63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101101-105709114", "type": "article", "title": "High-resolution spectroscopic study of red clump stars in the Galaxy: iron-group elements", "author": [ { "family_name": "Puzeras", "given_name": "E.", "clpid": "Puzeras-E" }, { "family_name": "Tautvai\u0161ien\u0117", "given_name": "G.", "clpid": "Tautvai\u0161ien\u0117-G" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Gray", "given_name": "D. F.", "clpid": "Gray-D-F" }, { "family_name": "Adelman", "given_name": "S. J.", "clpid": "Adelman-S-J" }, { "family_name": "Ilyin", "given_name": "I.", "clpid": "Ilyin-I" }, { "family_name": "Chorniy", "given_name": "Y.", "clpid": "Chorniy-Y" } ], "abstract": "The main atmospheric parameters and abundances of the iron-group elements (vanadium, chromium, iron, cobalt and nickel) are determined for 62 red giant 'clump' stars revealed in the Galactic field by the Hipparcos orbiting observatory. The stars form a homogeneous sample with the mean value of temperature T_(eff)= 4750 \u00b1 160 K, of surface gravity log g= 2.41 \u00b1 0.26 and the mean value of metallicity [Fe/H]=\u22120.04 \u00b1 0.15 dex. A Gaussian fit to the [Fe/H] distribution produces the mean \u3008[Fe/H]\u3009=\u22120.01 and dispersion \u03c3_([Fe/H])= 0.08. The near-solar metallicity and small dispersion of \u03c3_([Fe/H]) of clump stars of the Galaxy obtained in this paper confirm the theoretical model of the Hipparcos clump by Girardi & Salaris. This suggests that nearby clump stars are (in the mean) relatively young objects, reflecting mainly the near-solar metallicities developed in the local disc during the last few Gyr of its history. We find iron-group element to iron-abundance ratios in clump giants to be close to solar.", "doi": "10.1111/j.1365-2966.2010.17195.x", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "2010-10", "series_number": "2", "volume": "408", "issue": "2", "pages": "1225-1232" }, { "id": "authors:pq1wm-exr19", "collection": "authors", "collection_id": "pq1wm-exr19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100823-132646010", "type": "article", "title": "The Chemical Evolution of the Ursa Minor Dwarf Spheroidal Galaxy", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Huang", "given_name": "Wenjin", "clpid": "Huang-Wenjin" } ], "abstract": "We present an abundance analysis based on high-resolution spectra of 10 stars selected to span the full range in metallicity in the Ursa Minor (UMi) dwarf spheroidal (dSph) galaxy. We find that [Fe/H] for the sample stars ranges from \u20131.35 to \u20133.10 dex. Combining our sample with previously published work for a total of 16 luminous UMi giants, we establish the trends of abundance ratios [X/Fe] as functions of [Fe/H] for 15 elements. In key cases, particularly for the \u03b1-elements, these trends resemble those for stars in the outer part of the Galactic halo, especially at the lowest metallicities probed. The neutron-capture elements show an r-process distribution over the full range of Fe metallicity reached in this dSph galaxy. This suggests that the duration of star formation in the UMi dSph was shorter than in other dSph galaxies. The derived ages for a larger sample of UMi stars with more uncertain metallicities also suggest a population dominated by uniformly old (~13 Gyr) stars, with a hint of an age-metallicity relationship. Upon comparing our results for UMi, our earlier work in Draco, and published studies of more metal-rich dSph Galactic satellites, there appears to be a pattern of moving from a chemical inventory for dSph giants with [Fe/H] \u227e \u20132 dex, which is very similar to that of stars in the outer part of the Galactic halo (enhanced \u03b1/Fe relative to the Sun, coupled with subsolar [X/Fe] for the heavy neutron-capture elements and r-process domination), switching to subsolar \u03b1-elements and super-solar s-process-dominated neutron-capture elements for the highest [Fe/H] dSph stars. The combination of low star formation rates over a varying and sometimes extended duration that produced the stellar populations in the local dSph galaxies with [Fe/H] > \u2013 1.5 dex leads to a chemical inventory wildly discrepant from that of any component of the Milky Way. We note the presence of two UMi giants with [Fe/H] < \u20133.0 dex in our sample and reaffirm that the inner Galactic halo could have been formed by early accretion of Galactic satellite galaxies and dissolution of young globular clusters, while the outer halo could have formed from those satellite galaxies that accreted somewhat later.", "doi": "10.1088/0004-637X/719/1/931", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2010-08-10", "series_number": "1", "volume": "719", "issue": "1", "pages": "931-949" }, { "id": "authors:k2te8-1qp76", "collection": "authors", "collection_id": "k2te8-1qp76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100401-132857832", "type": "article", "title": "A Puzzle Involving Galactic Bulge Microlensing Events", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Gould", "given_name": "Andrew", "clpid": "Gould-A-P" }, { "family_name": "Thompson", "given_name": "Ian B.", "clpid": "Thompson-I-B" }, { "family_name": "Feltzing", "given_name": "Sophia", "clpid": "Feltzing-S" }, { "family_name": "Bensby", "given_name": "Thomas", "clpid": "Bensby-T" }, { "family_name": "Johnson", "given_name": "Jennifer A.", "clpid": "Johnson-Jennifer-A" }, { "family_name": "Huang", "given_name": "Wenjin", "clpid": "Huang-Wenjin" }, { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Lucatello", "given_name": "Sara", "clpid": "Lucatello-S" }, { "family_name": "Asplund", "given_name": "Martin", "clpid": "Asplund-M" } ], "abstract": "We study a sample of 16 microlensed Galactic bulge main-sequence turnoff region stars for which high-dispersion spectra have been obtained with detailed abundance analyses. We demonstrate that there is a very strong and highly statistically significant correlation between the maximum magnification of the microlensed bulge star and the value of the [Fe/H] deduced from the high resolution spectrum of each object. Physics demands that this correlation, assuming it to be real, be the result of some sample bias. We suggest several possible explanations, but are forced to reject them all, and are left puzzled. To obtain a reliable metallicity distribution in the Galactic bulge based on microlensed dwarf stars, it will be necessary to resolve this issue through the course of additional observations.", "doi": "10.1088/2041-8205/711/1/L48", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2010-03-01", "series_number": "1", "volume": "711", "issue": "1", "pages": "L48-L52" }, { "id": "authors:yw45g-x8729", "collection": "authors", "collection_id": "yw45g-x8729", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100413-105838778", "type": "article", "title": "An HST/WFPC2 survey of bright young clusters in M\u200931. IV. Age and mass estimates", "author": [ { "family_name": "Perina", "given_name": "S.", "clpid": "Perina-S" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Barmby", "given_name": "P.", "orcid": "0000-0003-2767-0090", "clpid": "Barmby-P" }, { "family_name": "Beasley", "given_name": "M. A.", "clpid": "Beasley-M-A" }, { "family_name": "Bellazzini", "given_name": "M.", "orcid": "0000-0001-8200-810X", "clpid": "Bellazzini-M" }, { "family_name": "Brodie", "given_name": "J. P.", "orcid": "0000-0002-9658-8763", "clpid": "Brodie-J-P" }, { "family_name": "Federici", "given_name": "L.", "clpid": "Federici-L" }, { "family_name": "Fusi Pecci", "given_name": "F.", "clpid": "Fusi-Pecci-F" }, { "family_name": "Galleti", "given_name": "S.", "clpid": "Galleti-S" }, { "family_name": "Hodge", "given_name": "P. W.", "clpid": "Hodge-P-W" }, { "family_name": "Huchra", "given_name": "J. P.", "clpid": "Huchra-J-P" }, { "family_name": "Kissler-Patig", "given_name": "M.", "clpid": "Kissler-Patig-M" }, { "family_name": "Puzia", "given_name": "T. H.", "orcid": "0000-0003-0350-7061", "clpid": "Puzia-T-H" }, { "family_name": "Strader", "given_name": "J.", "orcid": "0000-0002-1468-9668", "clpid": "Strader-J" } ], "abstract": "Aims. We present the main results of an imaging survey of possible young massive clusters (YMC) in M\u200931 performed with the Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST), with the aim of estimating their age and their mass. We obtained shallow (to B ~ 25) photometry of individual stars in 19 clusters (of the 20 targets of the survey). We present the images and color magnitude diagrams (CMDs) of all of our targets.\n\nMethods. Point spread function fitting photometry of individual stars was obtained for all the WFPC2 images of the target clusters, and the completeness of the final samples was estimated using extensive sets of artificial stars experiments. The reddening, age, and metallicity of the clusters were estimated by comparing the observed CMDs and luminosity functions (LFs) with theoretical models. Stellar masses were estimated by comparison with theoretical models in the (Age) vs. absolute integrated magnitude plane, using ages estimated from our CMDs and integrated J, H, K magnitudes from 2MASS-6X.\n\nResults. Nineteen of the twenty surveyed candidates were confirmed to be real star clusters, while one turned out to be a bright star. Three of the clusters were found not to be good YMC candidates from newly available integrated spectroscopy and were in fact found to be old from their CMD. Of the remaining sixteen clusters, fourteen have ages between 25 Myr and 280 Myr, two have older ages than 500 Myr (lower limits). By including ten other YMC with HST photometry from the literature, we assembled a sample of 25 clusters younger than 1 Gyr, with mass ranging from 0.6 \u00d7 10^4 M_\u2609 to 6 \u00d7 10^4 M_\u2609, with an average of ~3 \u00d7 10^4 M_\u2609. Our estimates of ages and masses well agree with recent independent studies based on integrated spectra.\n\nConclusions. The clusters considered here are confirmed to have masses significantly higher than Galactic open clusters (OC) in the same age range. Our analysis indicates that YMCs are relatively common in all the largest star-forming galaxies of the Local Group, while the lack of known YMC older than 20 Myr in the Milky Way may stem from selection effects.", "doi": "10.1051/0004-6361/200913459", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2010-02", "volume": "511", "pages": "A23" }, { "id": "authors:vzf91-tey16", "collection": "authors", "collection_id": "vzf91-tey16", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100303-092607636", "type": "article", "title": "A New Solution for the Dispersive Element in Astronomical Spectrographs", "author": [ { "family_name": "Epps", "given_name": "Harland W.", "clpid": "Epps-H-W" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Clemens", "given_name": "J. Christopher", "clpid": "Clemens-J-C" } ], "abstract": "We present a new solution for the dispersive element in astronomical spectrographs that, in many cases, can provide an upgrade path to enhance the spectral resolution of existing moderate-resolution reflection-grating spectrographs. We demonstrate that in the case of LRIS-R at the Keck 1 Telescope, a spectral resolution of 18,000 can be achieved with reasonable throughput under good seeing conditions.", "doi": "10.1086/650547", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "2010-02", "series_number": "888", "volume": "122", "issue": "888", "pages": "201-206" }, { "id": "authors:5a37n-73817", "collection": "authors", "collection_id": "5a37n-73817", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100107-145440365", "type": "article", "title": "A Hubble Space Telescope/WFPC2 Survey of Bright Young Clusters in M31. III. Structural Parameters", "author": [ { "family_name": "Barmby", "given_name": "P.", "orcid": "0000-0003-2767-0090", "clpid": "Barmby-P" }, { "family_name": "Perina", "given_name": "S.", "clpid": "Perina-S" }, { "family_name": "Bellazzini", "given_name": "M.", "orcid": "0000-0001-8200-810X", "clpid": "Bellazzini-M" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Hodge", "given_name": "P. W.", "clpid": "Hodge-P-W" }, { "family_name": "Huchra", "given_name": "J. P.", "clpid": "Huchra-J-P" }, { "family_name": "Kissler-Patig", "given_name": "M.", "clpid": "Kissler-Patig-M" }, { "family_name": "Puzia", "given_name": "T. H.", "orcid": "0000-0003-0350-7061", "clpid": "Puzia-T-H" }, { "family_name": "Strader", "given_name": "J.", "orcid": "0000-0002-1468-9668", "clpid": "Strader-J" } ], "abstract": "Surface brightness profiles for 23 M31 star clusters were measured using images from the Wide Field Planetary Camera 2 on the Hubble Space Telescope, and fitted to two types of models to determine the clusters' structural properties. The clusters are primarily young (~10^8 yr) and massive (~10^(4.5) M_\u2299), with median half-light radius 7 pc and dissolution times of a few Gyr. The properties of the M31 clusters are comparable to those of clusters of similar age in the Magellanic Clouds. Simulated star clusters are used to derive a conversion from statistical measures of cluster size to half-light radius so that the extragalactic clusters can be compared to young massive clusters in the Milky Way. All three sets of star clusters fall approximately on the same age-size relation. The young M31 clusters are expected to dissolve within a few Gyr and will not survive to become old, globular clusters. However, they do appear to follow the same fundamental plane (FP) relations as old clusters; if confirmed with velocity dispersion measurements, this would be a strong indication that the star cluster FP reflects universal cluster formation conditions.", "doi": "10.1088/0004-6256/138/6/1667", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2009-12", "series_number": "6", "volume": "138", "issue": "6", "pages": "1667-1680" }, { "id": "authors:s268r-awz34", "collection": "authors", "collection_id": "s268r-awz34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091208-093637563", "type": "article", "title": "Astrophysics: Assortment in the Galaxy", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Observations of star clusters in the Milky Way defy the view that the constituents of these systems are almost invariably chemically alike. The outlying clusters could be the tattered relics of once larger systems.", "doi": "10.1038/462421a", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2009-11-26", "series_number": "7272", "volume": "462", "issue": "7272", "pages": "421-422" }, { "id": "authors:1dgvt-7x693", "collection": "authors", "collection_id": "1dgvt-7x693", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091209-112919518", "type": "article", "title": "The stellar content of the Hamburg/ESO survey. V. The metallicity distribution function of the Galactic halo", "author": [ { "family_name": "Sch\u00f6rck", "given_name": "T.", "clpid": "Sch\u00f6rck-T" }, { "family_name": "Christlieb", "given_name": "N.", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Beers", "given_name": "T. C.", "orcid": "0000-0003-4573-6233", "clpid": "Beers-T-C" }, { "family_name": "Shectman", "given_name": "S.", "clpid": "Shectman-S" }, { "family_name": "Thompson", "given_name": "I.", "clpid": "Thompson-I" }, { "family_name": "McWilliam", "given_name": "A.", "clpid": "McWilliam-A" }, { "family_name": "Bessell", "given_name": "M. S.", "clpid": "Bessell-M-S" }, { "family_name": "Norris", "given_name": "J. E.", "clpid": "Norris-J-E" }, { "family_name": "Mel\u00e9ndez", "given_name": "J.", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Ram\u00edrez", "given_name": "S.", "clpid": "Ram\u00edrez-S" }, { "family_name": "Haynes", "given_name": "D.", "clpid": "Haynes-D" }, { "family_name": "Cass", "given_name": "P.", "clpid": "Cass-P" }, { "family_name": "Hartley", "given_name": "M.", "clpid": "Hartley-M" }, { "family_name": "Russell", "given_name": "K.", "clpid": "Russell-K" }, { "family_name": "Watson", "given_name": "F.", "clpid": "Watson-F" }, { "family_name": "Zickgraf", "given_name": "F.-J.", "clpid": "Zickgraf-F-J" }, { "family_name": "Behnke", "given_name": "B.", "clpid": "Behnke-B" }, { "family_name": "Fechner", "given_name": "C.", "clpid": "Fechner-C" }, { "family_name": "Fuhrmeister", "given_name": "B.", "clpid": "Fuhrmeister-B" }, { "family_name": "Barklem", "given_name": "P. S.", "clpid": "Barklem-P-S" }, { "family_name": "Edvardsson", "given_name": "B.", "clpid": "Edvardsson-B" }, { "family_name": "Frebel", "given_name": "A.", "orcid": "0000-0002-2139-7145", "clpid": "Frebel-A" }, { "family_name": "Wisotzki", "given_name": "L.", "clpid": "Wisotzki-L" }, { "family_name": "Reimers", "given_name": "D.", "clpid": "Reimers-D" } ], "abstract": "We determine the metallicity distribution function (MDF) of the Galactic halo by means of a sample of 1638 metal-poor stars selected from the Hamburg/ESO objective-prism survey (HES). The sample was corrected for minor biases introduced by the strategy for spectroscopic follow-up observations of the metal-poor candidates, namely \"best and brightest stars first\". Comparison of the metallicities [Fe/H] of the stars determined from moderate-resolution (i.e., R ~ 2000) follow-up spectra with results derived from abundance analyses based on high-resolution spectra (i.e., R > 20000) shows that the [Fe/H] estimates used for the determination of the halo MDF are accurate to within 0.3 dex, once highly C-rich stars are eliminated. We determined the selection function of the HES, which must be taken into account for a proper comparison between the HES MDF with MDFs of other stellar populations or those predicted by models of Galactic chemical evolution. The latter show a reasonable agreement with the overall shape of the HES MDF for [Fe/H] > \u22123.6, but only a model of Salvadori et al. (2007) with a critical metallicity for low-mass star formation of Z_(cr) = 10^(\u22123.4) Z_\u2609 reproduces the sharp drop at [Fe/H] \u223c \u22123.6 present in the HES MDF. Although currently about ten stars at [Fe/H] < \u22123.6 are known, the evidence for the existence of a tail of the halo MDF extending to [Fe/H] ~ \u22125.5 is weak from the sample considered in this paper, because it only includes two stars [Fe/H] < \u22123.6. Therefore, a comparison with theoretical models has to await larger statistically complete and unbiased samples. A comparison of the MDF of Galactic globular clusters and of dSph satellites to the Galaxy shows qualitative agreement with the halo MDF, derived from the HES, once the selection function of the latter is included. However, statistical tests show that the differences between these are still highly significant.", "doi": "10.1051/0004-6361/200810925", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2009-11", "series_number": "2", "volume": "507", "issue": "2", "pages": "817-832" }, { "id": "authors:xb1kw-e4k82", "collection": "authors", "collection_id": "xb1kw-e4k82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20091110-184457688", "type": "article", "title": "M31 Globular Cluster Abundances from High-Resolution, Integrated-Light Spectroscopy", "author": [ { "family_name": "Colucci", "given_name": "Janet E.", "clpid": "Colucci-J-E" }, { "family_name": "Bernstein", "given_name": "Rebecca A.", "clpid": "Bernstein-R-A" }, { "family_name": "Cameron", "given_name": "Scott", "clpid": "Cameron-S" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We report the first detailed chemical abundances for five globular clusters (GCs) in M31 from high-resolution (R ~ 25,000) spectroscopy of their integrated light (IL). These GCs are the first in a larger set of clusters observed as part of an ongoing project to study the formation history of M31 and its GC population. The data presented here were obtained with the HIRES echelle spectrograph on the Keck I telescope and are analyzed using a new IL spectra analysis method that we have developed. In these clusters, we measure abundances for Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Y, and Ba, ages \u226510 Gyr, and a range in [Fe/H] of \u20130.9 to \u20132.2. As is typical of Milky Way GCs, we find these M31 GCs to be enhanced in the \u03b1-elements Ca, Si, and Ti relative to Fe. We also find [Mg/Fe] to be low relative to other [\u03b1/Fe], and [Al/Fe] to be enhanced in the IL abundances. These results imply that abundances of Mg, Al (and likely O, Na) recovered from IL do display the inter- and intra-cluster abundance variations seen in individual Milky Way GC stars, and that special care should be taken in the future in interpreting low- or high-resolution IL abundances of GCs that are based on Mg-dominated absorption features. Fe-peak and the neutron-capture elements Ba and Y also follow Milky Way abundance trends. We also present high-precision velocity dispersion measurements for all five M31 GCs, as well as independent constraints on the reddening toward the clusters from our analysis.", "doi": "10.1088/0004-637X/704/1/385", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2009-10-10", "series_number": "1", "volume": "704", "issue": "1", "pages": "385-414" }, { "id": "authors:kgtv8-2wx24", "collection": "authors", "collection_id": "kgtv8-2wx24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090916-112836481", "type": "article", "title": "An HST/WFPC Survey of Bright Young Clusters in M31. II. Photometry of Less Luminous Clusters in the Fields", "author": [ { "family_name": "Hodge", "given_name": "P. W.", "clpid": "Hodge-P-W" }, { "family_name": "Krienke", "given_name": "O. K.", "clpid": "Krienke-O-K" }, { "family_name": "Bellazzini", "given_name": "M.", "orcid": "0000-0001-8200-810X", "clpid": "Bellazzini-M" }, { "family_name": "Perina", "given_name": "S.", "clpid": "Perina-S" }, { "family_name": "Barmby", "given_name": "P.", "orcid": "0000-0003-2767-0090", "clpid": "Barmby-P" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Puzia", "given_name": "T. H.", "orcid": "0000-0003-0350-7061", "clpid": "Puzia-T-H" }, { "family_name": "Strader", "given_name": "J.", "orcid": "0000-0002-1468-9668", "clpid": "Strader-J" } ], "abstract": "We report on the properties of 89 low-mass star clusters located in the vicinity of luminous young clusters (\"blue globulars\") in the disk of M31. Eighty-two of the clusters are newly detected. We have determined their integrated magnitudes and colors, based on a series of Hubble Space Telescope (HST)/Wide Field Planetary Camera 2 exposures in blue and red (HST filters F450W and F814W). The integrated apparent magnitudes range from F450W = 17.5 to 22.5, and the colors indicate a wide range of ages. Stellar color-magnitude diagrams for all clusters were obtained and those with bright enough stars were fit to theoretical isochrones to provide age estimates. The ages range from 12 Myr to >500 Myr. Reddenings, which average E(F450 \u2013 F814) = 0.59 with a dispersion of 0.21 mag, were derived from the main-sequence fitting for those clusters. Comparison of these ages and integrated colors with single population theoretical models with solar abundances suggests a color offset of 0.085 mag at the ages tested. Estimated ages for the remaining clusters are based on their measured colors. The age-frequency diagram shows a steep decline of number with age, with a large decrease in number per age interval between the youngest and the oldest clusters detected.", "doi": "10.1088/0004-6256/138/3/770", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2009-09", "series_number": "3", "volume": "138", "issue": "3", "pages": "770-779" }, { "id": "authors:prwrt-ptg76", "collection": "authors", "collection_id": "prwrt-ptg76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090825-113042555", "type": "article", "title": "The Chemical Evolution of the Draco Dwarf Spheroidal Galaxy", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Huang", "given_name": "Wenjin", "clpid": "Huang-Wenjin" } ], "abstract": "We present an abundance analysis based on high-resolution spectra of eight stars selected to span the full range in metallicity in the Draco dwarf spheroidal (dSph) galaxy. We find that [Fe/H] for the sample stars ranges from \u20131.5 to \u20133.0 dex. Combining our sample with previously published work for a total of 14 luminous Draco giants, we show that the abundance ratios [Na/Fe], [Mg/Fe], and [Si/Fe] for the Draco giants overlap those of Galactic halo giants at the lowest [Fe/H] probed, but are significantly lower for the higher Fe-metallicity Draco stars. For the explosive \u03b1-elements Ca and Ti, the abundance ratios for Draco giants with [Fe/H] > \u2013 2.4 dex are approximately constant and slightly subsolar, well below values characteristic of Galactic halo stars. The s-process contribution to the production of heavy elements begins at significantly lower Fe metallicity than in the Galactic halo. Using a toy model we compare the behavior of the abundance ratios within the sample of Draco giants with those from the literature of Galactic globular clusters, and the Carina and Sgr dSph galaxies. The differences appear to be related to the timescale for buildup of the heavy elements, with Draco having the slowest rate. We note the presence of a Draco giant with [Fe/H] <\u20133.0 dex in our sample, and reaffirm that the inner Galactic halo could have been formed by early accretion of Galactic satellite galaxies and dissolution of young globular clusters, while the outer halo could have formed from those satellite galaxies accreted later.", "doi": "10.1088/0004-637X/701/2/1053", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2009-08-20", "series_number": "2", "volume": "701", "issue": "2", "pages": "1053-1075" }, { "id": "authors:xmkhh-mp657", "collection": "authors", "collection_id": "xmkhh-mp657", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20101101-112231015", "type": "book_section", "title": "Globular cluster abundances and what they can tell us about galaxy formation", "book_title": "Star clusters: basic galactic building blocks throughout time and space", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "DeGrijs", "given_name": "R.", "clpid": "DeGrijs-R" }, { "family_name": "Lepine", "given_name": "J. R. D.", "clpid": "Lepine-J-R-D" } ], "abstract": "We review the properties of globular clusters (GCs) which make them useful for studying the Galactic halo, Galactic chemical evolution and the early stages of the formation of the Milky Way. We review the evidence that GCs have a chemical inventory similar to those of halo field stars. We discuss the abundance ratios for dSph galaxies and show that it is possible to have formed at least part of the Galactic-halo field stellar population by dissolving GCs and/or accreting dSph galaxies, but only if this occurred at an early stage in the formation of the Galaxy. We review the constraints on halo-formation timescales deduced from the low magnesium isotopic ratios in metal-poor halo field dwarfs, which indicate that asymptotic giant-branch (AGB) stars did not have time to contribute significantly, while M71 contains two populations, one without and also one with a substantial AGB contribution. We review the limited evidence for GCs with a second population showing additional contributions from Type II supernovae, currently confined to \u03c9 Cen, M54 and M22, all of which may have been the nuclei or central regions of accreted galaxies. We check our own data for additional similar GCs and find preliminary indications that NGC 2419, a massive GC far in the outer Galactic halo, may also belong to this group.", "doi": "10.1017/S1743921309990998", "isbn": "9780-521-76484-1", "publisher": "Cambridge University Press", "place_of_publication": "Cambridge", "publication_date": "2009-08", "pages": "149-156" }, { "id": "authors:ck9ys-z2a53", "collection": "authors", "collection_id": "ck9ys-z2a53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090911-085647053", "type": "article", "title": "The Rise of the AGB in the Galactic Halo: Mg Isotopic Ratios and High Precision Elemental Abundances in M71 Giants", "author": [ { "family_name": "Mel\u00e9ndez", "given_name": "J.", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "High-resolution (R \u2248 100,000), high signal-to-noise spectra of M71 giants have been obtained with High Resolution Echelle Spectrometer at the Keck I telescope in order to measure their Mg isotopic ratios, as well as elemental abundances of C, N, O, Na, Mg, Al, Si, Ca, Ti, Ni, Zr, and La. We demonstrate that M71 has two populations, the first having weak CN, normal O, Na, Mg, and Al, and a low ratio of ^(26)Mg/Mg (~4%) consistent with models of galactic chemical evolution with no contribution from asymptotic giant branch (AGB) stars. The Galactic halo could have been formed from the dissolution of globular clusters prior to their intermediate-mass stars reaching the AGB. The second population has enhanced Na and Al accompanied by lower O and by higher ^(26)Mg/Mg (~8%), consistent with models which do incorporate ejecta from AGB stars via normal stellar winds. All the M71 giants have identical [Fe/H], [Si/Fe], [Ca/Fe], [Ti/Fe], and [Ni/Fe] to within \u03c3 = 0.04 dex (10%). We therefore infer that the timescale for formation of the first generation of stars we see today in this globular cluster must be sufficiently short to avoid a contribution from AGB stars, i.e., less than ~0.3 Gyr. Furthermore, the Mg isotopic ratios in the second M71 population, combined with their elemental abundances for the light elements, demonstrate that the difference must be the result of adding in the ejecta of intermediate-mass AGB stars. Finally, we suggest that the low amplitude of the abundance variations of the light elements within M71 is due to a combination of its low mass and its relatively high Fe-metallicity.", "doi": "10.1088/0004-637X/699/2/2017", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2009-07-10", "series_number": "2", "volume": "699", "issue": "2", "pages": "2017-2025" }, { "id": "authors:t1cbv-cfn03", "collection": "authors", "collection_id": "t1cbv-cfn03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090819-100854699", "type": "article", "title": "Clues to the Metallicity Distribution in the Galactic Bulge: Abundances in MOA-2008-BLG-310S and MOA-2008-BLG-311S", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Thompson", "given_name": "Ian B.", "clpid": "Thompson-I-B" }, { "family_name": "Sumi", "given_name": "Takahiro", "clpid": "Sumi-Takahiro" }, { "family_name": "Bond", "given_name": "Ian", "clpid": "Bond-I" }, { "family_name": "Gould", "given_name": "Andrew", "clpid": "Gould-A-P" }, { "family_name": "Johnson", "given_name": "Jennifer A.", "orcid": "0000-0001-9808-7172", "clpid": "Johnson-J-A" }, { "family_name": "Huang", "given_name": "Wenjin", "clpid": "Huang-Wenjin" }, { "family_name": "Burley", "given_name": "Greg", "clpid": "Burley-G" } ], "abstract": "We present abundance analyses based on high dispersion and high signal-to-noise ratio Magellan spectra of two highly microlensed Galactic bulge stars in the region of the main-sequence turnoff with T_(eff) ~ 5650 K. We find that MOA-2008-BLG-310S has [Fe/H]^8 = +0.41 \u00b1 0.09 dex. We adopt the usual spectroscopic notations that [A/B] \u2261log_(10)(N_A /N_B )^* \u2013 log_10(N_A /N_B )_\u2299, and that log[\u0454(A)] \u2261 log_10(N_A /N_H ) + 12.00, for elements A and B. and MOA-2008-BLG-311S has +0.26 \u00b1 0.09 dex. The abundance ratios for the ~20 elements for which features could be detected in the spectra of each of the two stars follow the trends with [Fe/H] found among samples of bulge giants. Combining these two bulge dwarfs with the results from previous abundance analysis of four other Galactic bulge turnoff region stars, all highly magnified by microlensing, gives a mean [Fe/H] of +0.29 dex. This implies that there is an inconsistency between the Fe-metallicity distribution of the microlensed bulge dwarfs and that derived by the many previous estimates based on surveys of cool, luminous bulge giants, which have mean [Fe/H] ~ \u20130.1 dex. A number of possible mechanisms for producing this difference are discussed. If one ascribes this inconsistency to systematic errors in the abundance analyses, we provide statistical arguments suggesting that a substantial systematic error in the Fe metallicity for one or both of the two cases, bulge dwarfs versus bulge giants, is required which is probably larger than can realistically be accommodated.", "doi": "10.1088/0004-637X/699/1/66", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2009-07-01", "series_number": "1", "volume": "699", "issue": "1", "pages": "66-75" }, { "id": "authors:29gwy-d6907", "collection": "authors", "collection_id": "29gwy-d6907", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090714-144013466", "type": "article", "title": "Chemical evolution of the Galactic bulge as traced by microlensed dwarf and subgiant stars. Detailed abundance analysis of OGLE-2008-BLG-209S", "author": [ { "family_name": "Bensby", "given_name": "T.", "clpid": "Bensby-T" }, { "family_name": "Johnson", "given_name": "J. A.", "orcid": "0000-0001-9808-7172", "clpid": "Johnson-J-A" }, { "family_name": "Cohen", "given_name": "J.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Feltzing", "given_name": "S.", "clpid": "Feltzing-S" }, { "family_name": "Udalski", "given_name": "A.", "orcid": "0000-0001-5207-5619", "clpid": "Udalski-A" }, { "family_name": "Gould", "given_name": "A.", "clpid": "Gould-A" }, { "family_name": "Huang", "given_name": "W.", "clpid": "Huang-Wenjin" }, { "family_name": "Thompson", "given_name": "I.", "clpid": "Thompson-I" }, { "family_name": "Simmerer", "given_name": "J.", "clpid": "Simmerer-J" }, { "family_name": "Ad\u00e9n", "given_name": "D.", "clpid": "Ad\u00e9n-D" } ], "abstract": "Aims. Our aims are twofold. First we aim to evaluate the robustness and accuracy of stellar parameters and detailed elemental abundances that can be derived from high-resolution spectroscopic observations of microlensed dwarf and subgiant stars. We then aim to use microlensed dwarf and subgiant stars to investigate the abundance structure and chemical evolution of the Milky Way Bulge. Contrary to the cool giant stars, with their extremely crowded spectra, the dwarf stars are hotter, their spectra are cleaner, and the elemental abundances of the atmospheres of dwarf and subgiant stars are largely untouched by the internal nuclear processes of the star.\nMethods. We present a detailed elemental abundance analysis of OGLE-2008-BLG-209S, the source star of a new microlensing event towards the Bulge, for which we obtained a high-resolution spectrum with the MIKE spectrograph on the Magellan Clay telescope. We have performed four different analyses of OGLE-2008-BLG-209S. One method is identical to the one used for a large comparison sample of F and G dwarf stars, mainly thin and thick disc stars, in the Solar neighbourhood. We have also re-analysed three previous microlensed dwarf stars OGLE-2006-BLG-265S, MOA-2006-BLG-099S, and OGLE-2007-BLG-349S with the same method. This homogeneous data set, although small, enables a direct comparison between the different stellar populations.\nResults. We find that OGLE-2008-BLG-209S is a subgiant star that has a metallicity of [Fe/H] \u2248 -0.33. It possesses [\u03b1/Fe] enhancements similar to what is found for Bulge giant stars at the same metallicity, and what also is found for nearby thick disc stars at the same metallicity. In contrast, the previous three microlensing dwarf stars have very high metallicities, [Fe/H] \u2273 +0.4, and more solar-like abundance ratios, i.e. [\u03b1/Fe] \u2248 0. The decrease in the [\u03b1/Fe] ratio with [Fe/H] is the typical signature of enrichment from low and intermediate mass stars. We furthermore find that the results for the four Bulge stars, in combination with results from studies of giant stars in the Bulge, seem to favour a secular formation scenario for the Bulge.", "doi": "10.1051/0004-6361/200911629", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2009-06-01", "series_number": "3", "volume": "499", "issue": "3", "pages": "737-753" }, { "id": "authors:dxp7f-2xr45", "collection": "authors", "collection_id": "dxp7f-2xr45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090924-100205487", "type": "article", "title": "An HST/WFPC2 survey of bright young clusters in M31. I. VdB0, a massive star cluster seen at t \u2243 25 Myr", "author": [ { "family_name": "Perina", "given_name": "S.", "clpid": "Perina-S" }, { "family_name": "Barmby", "given_name": "P.", "orcid": "0000-0003-2767-0090", "clpid": "Barmby-P" }, { "family_name": "Beasley", "given_name": "M. A.", "clpid": "Beasley-M-A" }, { "family_name": "Bellazzini", "given_name": "M.", "orcid": "0000-0001-8200-810X", "clpid": "Bellazzini-M" }, { "family_name": "Brodie", "given_name": "J. P.", "orcid": "0000-0002-9658-8763", "clpid": "Brodie-J-P" }, { "family_name": "Burstein", "given_name": "D.", "clpid": "Burstein-D" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Federici", "given_name": "L.", "clpid": "Federici-L" }, { "family_name": "Fusi-Pecci", "given_name": "F.", "clpid": "Fusi-Pecci-F" }, { "family_name": "Galleti", "given_name": "S.", "clpid": "Galleti-S" }, { "family_name": "Hodge", "given_name": "P. W.", "clpid": "Hodge-P-W" }, { "family_name": "Huchra", "given_name": "J. P.", "clpid": "Huchra-J-P" }, { "family_name": "Kissler-Patig", "given_name": "M.", "clpid": "Kissler-Patig-M" }, { "family_name": "Puzia", "given_name": "T. H.", "orcid": "0000-0003-0350-7061", "clpid": "Puzia-T-H" }, { "family_name": "Strader", "given_name": "J.", "orcid": "0000-0002-1468-9668", "clpid": "Strader-J" } ], "abstract": "Aims. We introduce our imaging survey of possible young massive globular clusters in M31 performed with the Wide Field and Planetary Camera 2 (WFPC2) on the Hubble Space Telescope (HST). We obtained shallow (to B ~ 25) photometry of individual stars in 20 candidate clusters. We present here details of the data reduction pipeline that is being applied to all the survey data and describe its application to the brightest among our targets, van den Bergh 0 (VdB0), taken as a test case.\nMethods. Point spread function fitting photometry of individual stars was obtained for all the WFPC2 images of VdB0 and the completeness of the final samples was estimated using an extensive set of artificial stars experiments. The reddening, the age and the metallicity of the cluster were estimated by comparing the observed color magnitude diagram (CMD) with theoretical isochrones. Structural parameters were obtained from model-fitting to the intensity profiles measured within circular apertures on the WFPC2 images.\nResults. Under the most conservative assumptions, the stellar mass of VdB0 is M> 2.4 x 10^4 M_\u2609 , but our best estimates lie in the range \u22434-9 x 10^4 M_\u2609. The CMD of VdB0 is best reproduced by models having solar metallicity and age \u224325 Myr. Ages less than \u224312 Myr and greater than \u224360 Myr are clearly ruled out by the available data. The cluster has a remarkable number of red super giants (\u227318) and a CMD very similar to Large Magellanic Cloud clusters usually classified as young globulars such as NGC 1850, for example.\nConclusions. VdB0 is significantly brighter (\u22731 mag) than Galactic open clusters of similar age. Its present-day mass and half-light radius ((r_h = 7.4 pc) are more typical of faint globular clusters than of open clusters. However, given its position within the disk of M31, it is expected to be destroyed by dynamical effects, in particular by encounters with giant molecular clouds, within the next ~4 Gyr.", "doi": "10.1051/0004-6361:200810725", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2009-02", "series_number": "3", "volume": "494", "issue": "3", "pages": "933-948" }, { "id": "authors:dv41z-5c870", "collection": "authors", "collection_id": "dv41z-5c870", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-085930794", "type": "publication_whitepaper", "title": "The Chemical Evolution of the Galactic Bulge", "author": [ { "family_name": "Rich", "given_name": "R. Michael", "orcid": "0000-0003-0427-8387", "clpid": "Rich-R-M" }, { "family_name": "Clarkson", "given_name": "Will", "clpid": "Clarkson-W-I" }, { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Howard", "given_name": "Christian", "clpid": "Howard-C" }, { "family_name": "McWilliam", "given_name": "Andy", "clpid": "McWilliam-A" }, { "family_name": "Johnson", "given_name": "Jennifer", "clpid": "Johnson-Jennifer-A" }, { "family_name": "Johnson", "given_name": "Christian", "clpid": "Johnson-C-I" }, { "family_name": "Cunha", "given_name": "Katia", "clpid": "Cunha-K" }, { "family_name": "Smith", "given_name": "Verne", "clpid": "Smith-V-V" }, { "family_name": "Fulbright", "given_name": "Jon", "clpid": "Fulbright-J" } ], "abstract": "This science white paper addresses the issue of discovering the chemical evolution of the\nGalactic bulge, from which we may learn the initial mass function at the time of the formation of\nthe bulge, the timescale for the initial burst of star formation, any evidence supporting an\nextended era of star formation, evidence of very early mergers of massive subcomponents, and\nthe fraction of its mass that was contributed by late mergers. A further immediate problem\nconcerns the composition of dwarfs measured from microlensing events versus the abundance\nscale measured from giants. A companion White Paper (Clarkson & Rich) addresses a set of\nbulge science questions that require observations at very high angular resolution.", "publisher": "Caltech Library", "publication_date": "2009" }, { "id": "authors:e553m-qkm70", "collection": "authors", "collection_id": "e553m-qkm70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100511-100205127", "type": "book_section", "title": "IR Integrated Light Colors For Galactic GCs and An Update on Young M31 Globular Clusters", "book_title": "Globular Clusters - Guides to Galaxies", "author": [ { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Richtler", "given_name": "Tom", "clpid": "Richtler-T" }, { "family_name": "Larsen", "given_name": "S\u00f8ren", "clpid": "Larsen-S-S" } ], "abstract": "In our recent publication, Cohen, Matthews and Cameron [3], we presented observations made with the newly commissioned Keck laser-guide star adaptive optics system of 6 objects in M31 that are alleged in multiple recent studies to be young globular clusters (GCs); all are supposed to have ages\n\u22645 Gyr. The resulting FWHM of the PSF core in our images was ~70 mas. The four youngest of these objects are asterisms; they are with certainty not young GCs in M31. Based on their morphology, the two oldest are GCs in\nM31. While the M31 GCs with ages 5\u20138 Gyr appear to be mostly genuine, it appears that many of the alleged very young GCs in M31 are spurious identifications. This problem will be even more severe in studies of the GC systems of more distant spiral galaxies now underway, for which imaging at the spatial resolution of our observations in M31 may not be adequate to detect sample contamination by asterisms.\nHere we provide a brief update for this work.", "doi": "10.1007/978-3-540-76961-3_45", "isbn": "978-3-540-76960-6", "publisher": "Springer", "place_of_publication": "New York, NY", "publication_date": "2009", "pages": "189-192" }, { "id": "authors:1v9x3-sdp33", "collection": "authors", "collection_id": "1v9x3-sdp33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-134859287", "type": "article", "title": "Clues to the Metallicity Distribution in the Galactic Bulge: Abundances in OGLE-2007-BLG-349S", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Huang", "given_name": "Wenjin", "clpid": "Huang-Wenjin" }, { "family_name": "Udalski", "given_name": "A.", "orcid": "0000-0001-5207-5619", "clpid": "Udalski-A" }, { "family_name": "Gould", "given_name": "Andrew", "clpid": "Gould-A-P" }, { "family_name": "Johnson", "given_name": "Jennifer A.", "orcid": "0000-0001-9808-7172", "clpid": "Johnson-J-A" } ], "abstract": "We present an abundance analysis based on high-dispersion and high signal-to-noise ratio Keck spectra of a very highly microlensed Galactic bulge dwarf, OGLE-2007-BLG-349S, with T_(eff) ~ 5400 K. The amplification at the time the spectra were taken ranged from 350 to 450. This bulge star is highly enhanced in metallicity with [Fe/H ] = + 0.51 \u00b1 0.09 dex. The abundance ratios for the 28 species of 26 elements for which features could be detected in the spectra are almost all solar. In particular, there is no evidence for enhancement of any of the \u03b1-elements, including O and Mg. We conclude that the high [Fe/H] seen in this star, when combined with the equally high [Fe/H] derived in previous detailed abundance analysis of two other Galactic bulge dwarfs, both also highly magnified by microlensing, implies that the median metallicity in the Galactic bulge is very high. We thus infer that many previous estimates of the metallicity distribution in the Galactic bulge have substantially underestimated the mean Fe metallicity there due to sample bias, and suggest a candidate mechanism for such. If our conjecture proves valid, it may be necessary to update the calibrations for the algorithms used by many groups to interpret spectra and broadband photometry of the integrated light of very metal-rich old stellar populations, including luminous elliptical galaxies.", "doi": "10.1086/589143", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2008-08-01", "series_number": "2", "volume": "682", "issue": "2", "pages": "1029-1040" }, { "id": "authors:e7qrb-6qn28", "collection": "authors", "collection_id": "e7qrb-6qn28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180828-122926622", "type": "book_section", "title": "Abundances in Galactic Bulge Dwarfs and the Origin of the Elements in the Bulge", "author": [ { "family_name": "Johnson", "given_name": "Jeniffer A.", "orcid": "0000-0001-9808-7172", "clpid": "Johnson-J-A" }, { "family_name": "Gould", "given_name": "Andrew", "clpid": "Gould-A-P" }, { "family_name": "Gaudi", "given_name": "B. Scott", "orcid": "0000-0003-0395-9869", "clpid": "Gaudi-B-S" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Huang", "given_name": "Wenjin", "clpid": "Huang-Wenjin" }, { "family_name": "Gal-Yam", "given_name": "Avishay", "orcid": "0000-0002-3653-5598", "clpid": "Gal-Yam-A" }, { "family_name": "Leonard", "given_name": "Douglas C.", "clpid": "Leonard-D-C" }, { "family_name": "Simon", "given_name": "Joshua D.", "clpid": "Simon-J-D" }, { "family_name": "Udalski", "given_name": "Andrzej", "orcid": "0000-0001-5207-5619", "clpid": "Udalski-A" }, { "family_name": "Bond", "given_name": "Ian A.", "clpid": "Bond-I-A" }, { "family_name": "Sumi", "given_name": "Takahiro", "clpid": "Sumi-Takahiro" } ], "abstract": "The Galactic Bulge has a very different chemical evolution history than the Milky Way disk or halo. The unique mix of supernovae and asymptotic giant branch stars that have contributed to the elements in the bulge offer the opportunity to identify or confirm the nucleosynthesis sites of elements. Abundance measurements based on the spectra of Galactic bulge dwarfs provide the only reliable measurements of the evolution of C and N in the Bulge, and have also been the source of the first measurements of S, K, Zn, Cu and Ba. We report on the use of gravitational microlensing to observe very faint Galactic bulge dwarfs and discuss the implications of these measurements for the origin of the elements. In particular, we argue that Type Ia SNe are unlikely to be important sources of Zn, but while the data on C and N suggest that asymptotic giant stars contributed to the chemical enrichment of the bulge, the data on Ba suggest that there was a delay before substantial AGB star production.", "doi": "10.22323/1.053.0024", "publisher": "SISSA", "publication_date": "2008-08" }, { "id": "authors:tbbfk-m5461", "collection": "authors", "collection_id": "tbbfk-m5461", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190516-142246247", "type": "book_section", "title": "MAGIQ at the W. M. Keck Observatory: initial deployment of a new acquisition, guiding, and image quality monitoring system", "book_title": "Ground-based and Airborne Instrumentation for Astronomy II", "author": [ { "family_name": "Adkins", "given_name": "Sean M.", "clpid": "Adkins-S-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Aycock", "given_name": "Joel", "clpid": "Aycock-J" }, { "family_name": "Bell", "given_name": "James", "orcid": "0000-0002-2006-4074", "clpid": "Bell-J-F-III" }, { "family_name": "Cohen", "given_name": "Richard", "clpid": "Cohen-R-W" }, { "family_name": "Cooper", "given_name": "Andrew", "clpid": "Cooper-A-P" }, { "family_name": "Goodrich", "given_name": "Bob", "clpid": "Goodrich-B" }, { "family_name": "Johnson", "given_name": "Jimmy", "clpid": "Johnson-J" }, { "family_name": "Kwok", "given_name": "Shui H.", "clpid": "Kwok-Shui-H" }, { "family_name": "Lyke", "given_name": "Jim", "clpid": "Lyke-J" }, { "family_name": "McCann", "given_name": "Kevin", "clpid": "McCann-K" }, { "family_name": "Neyman", "given_name": "Chris", "clpid": "Neyman-C-R" }, { "family_name": "Nordin", "given_name": "Tom", "clpid": "Nordin-T" }, { "family_name": "Panteleev", "given_name": "Sergey", "clpid": "Panteleev-S" }, { "family_name": "Tolleth", "given_name": "Grant", "clpid": "Tolleth-G" }, { "family_name": "Tsubota", "given_name": "Myrna", "clpid": "Tsubota-Myrna" } ], "contributor": [ { "family_name": "McLean", "given_name": "Ian S.", "clpid": "McLean-I-S" }, { "family_name": "Casali", "given_name": "Mark M.", "clpid": "Casali-M-M" } ], "abstract": "The W. M. Keck Observatory has completed the development and initial deployment of MAGIQ, the Multi-function Acquisition, Guiding and Image Quality monitoring system. MAGIQ is an integrated system for acquisition, guiding and image quality measurement for the Keck telescopes. This system replaces the acquisition and guiding hardware and software for existing instruments at the Observatory and is now the standard for visible wavelength band acquisition cameras for future instrumentation. In this paper we report on the final design and implementation of this new system, which includes three major components: a visible wavelength band acquisition camera, image quality measurement capability, and software for acquisition, guiding and image quality monitoring. The overall performance is described, as well as the details of our approach to integrating low order wavefront sensing capability in order to provide closed loop control of telescope focus.", "doi": "10.1117/12.789857", "isbn": "9780819472243", "publisher": "Society of Photo-Optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "2008-07-09", "pages": "Art. No. 70141U" }, { "id": "authors:1qgkk-31n26", "collection": "authors", "collection_id": "1qgkk-31n26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160422-103841891", "type": "book_section", "title": "Magnesium Isotopes in Halo Stars", "book_title": "First stars III", "author": [ { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-Jorge" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "O'Shea", "given_name": "Brian W.", "clpid": "O'Shea-Brian-W" }, { "family_name": "Heger", "given_name": "Alexander", "clpid": "Heger-Alexander" }, { "family_name": "Abel", "given_name": "Tom G.", "clpid": "Abel-Tom-G" } ], "abstract": "We have determined Mg isotope ratios in halo field dwarfs and giants in the globular cluster M71 based on high S/N high spectral resolution (R\u2009=\u200910^5) Keck HIRES spectra. Unlike previous claims of an important contribution from intermediate\u2010mass AGB stars to the Galactic halo, we find that our ^(26)Mg/^(24) Mg ratios can be explained by massive stars.", "doi": "10.1063/1.2905536", "isbn": "978-0-7354-0509-7", "publisher": "American Institute of Physics", "place_of_publication": "Melville, NY", "publication_date": "2008-03-11", "pages": "181-183" }, { "id": "authors:tfaj1-q4x11", "collection": "authors", "collection_id": "tfaj1-q4x11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100707-132658295", "type": "book_section", "title": "An Update on the 0Z Project", "book_title": "First stars III : Santa Fe, New Mexico, 15-20 July 2007", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "N.", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "McWilliam", "given_name": "A.", "clpid": "McWilliam-A" }, { "family_name": "Shectman", "given_name": "S.", "clpid": "Shectman-S" }, { "family_name": "Thompson", "given_name": "I.", "clpid": "Thompson-I" } ], "abstract": "We give an update on our 0Z Survey to find more extremely metal poor (EMP) stars with [Fe/H]<\u22123 dex through mining the database of the Hamburg/ESO Survey. We present the most extreme such stars we have found from ~1550 moderate resolution follow up spectra. One of these, HE1424\u20130241, has highly anomalous abundance ratios not seen in any previously known halo giant, with very deficient Si, moderately deficient Ca and Ti, highly enhanced Mn and Co, and low C, all with respect to Fe. We suggest a SNII where the nucleosynthetic yield for explosive \u03b1\u2013burning nuclei was very low compared to that for the hydrostatic \u03b1\u2013burning element Mg, which is normal in this star relative to Fe. A second, less extreme, outlier star with high [Sc/Fe] has also been found.We examine the extremely metal-poor tail of the HES metallicity distribution function (MDF). We suggest on the basis of comparison of our high resolution detailed abundance analyses with [Fe/H](HES) for stars in our sample that the MDF inferred from follow up spectra of the HES sample of candidate EMP stars is heavily contaminated for [Fe/H](HES) <\u22123 dex; many of the supposed EMP stars below that metallicity are of substantially higher Fe-metallicity, including most of the very C-rich stars, or are spurious objects.", "doi": "10.1063/1.2905516", "isbn": "978-0-7354-0509-7", "publisher": "American Institute of Physics", "place_of_publication": "Melville, NY", "publication_date": "2008-03-11", "pages": "118-121" }, { "id": "authors:z8xsv-nxw91", "collection": "authors", "collection_id": "z8xsv-nxw91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20090617-201405721", "type": "article", "title": "New extremely metal-poor stars in the Galactic halo", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Shectman", "given_name": "Stephen", "clpid": "Shectman-S" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" }, { "family_name": "Melendez", "given_name": "Jorge", "clpid": "Melendez-J" }, { "family_name": "Wisotzki", "given_name": "Lutz", "clpid": "Wisotzki-L" }, { "family_name": "Reimers", "given_name": "Dieter", "clpid": "Reimers-D" } ], "abstract": "We present a detailed abundance analysis based on high-resolution and high signal-to-noise spectra of eight extremely metal-poor (EMP) stars with [ Fe/H ] \u227e \u2212 3.5 dex, four of which are new. Only stars with 4900 K < T_(eff) < 5650 K are included. Two stars of the eight are outliers in each of several abundance ratios. The most metal-poor star in this sample, HE 1424\u20130241, has [ Fe/H ] ~ \u2212 4 dex and is thus among the most metal-poor stars known in the Galaxy. It has highly anomalous abundance ratios unlike those of any other known EMP giant, with very low Si, Ca, and Ti relative to Fe, and enhanced Mn and Co, again relative to Fe. Only (low) upper limits for C and N can be derived from the nondetection of the CH and NH molecular bands. HE 0132-2429, another sample star, has excesses of N and Sc with respect to Fe. The strong outliers in abundance ratios among the Fe-peak elements in these C-normal stars, not found at somewhat higher metallicities ([ Fe/H ] ~ \u2212 3 dex), are definitely real. They suggest that at such low metallicities we are beginning to see the anticipated and long sought stochastic effects of individual supernova events contributing to the Fe-peak material within a single star. With spectra reaching well into the near-UV we are able to probe the behavior of copper abundances in such extreme EMP stars. A detailed comparison of the results of the analysis procedures adopted by our 0Z project compared to those of the First Stars VLT Large Project finds a systematic difference for [ Fe/H ] of ~0.3 dex, our values always being higher.", "doi": "10.1086/523638", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2008-01-01", "series_number": "1", "volume": "672", "issue": "1", "pages": "320-341" }, { "id": "authors:adxh5-ehf87", "collection": "authors", "collection_id": "adxh5-ehf87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:COHapjl07a", "type": "article", "title": "A new type of extremely metal-poor star", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Shectman", "given_name": "Stephen", "clpid": "Shectman-S" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" }, { "family_name": "Melendez", "given_name": "Jorge", "clpid": "Melendez-J" }, { "family_name": "Wisotzki", "given_name": "Lutz", "clpid": "Wisotzki-L" }, { "family_name": "Reimers", "given_name": "Dieter", "clpid": "Reimers-D" } ], "abstract": "We present an abundance analysis for the extremely metal-poor (EMP) star HE 1424-0241 based on high-dispersion spectra from HIRES at Keck. This star is a giant on the lower red giant branch with [Fe/H] ~ -4.0 dex. Relative to Fe, HE 1424-0241 has normal Mg, but it shows a very large deficiency of Si, with \u03b5(Si)/\u03b5(Fe) ~ 1/10 and \u03b5(Si)/\u03b5(Mg) ~ 1/25 that of all previously known EMP giants or dwarfs. It also has a moderately large deficiency of Ca and a smaller deficit of Ti, combined with enhanced Mn and Co and normal or low C. We suggest that in HE 1424-0241 we see the effect of a very small number of contributing supernovae, and that the SNe II contributing to the chemical inventory of HE 1424-0241 were biased in progenitor mass or in explosion characteristics so as to reproduce its abnormal extremely low Si/Mg ratio. HE 1424-0241 shows a deficiency of the explosive \u03b1-burning elements Si, Ca, and Ti coupled with a ratio [Mg/Fe] normal for EMP stars; Mg is produced via hydrostatic \u03b1-burning. The latest models of nucleosynthesis in SNe II fail to reproduce the abundance ratios seen in HE 1424-0241 for any combination of the parameter space of core-collapse explosions they explore.", "doi": "10.1086/518031", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2007-04-20", "series_number": "2", "volume": "659", "issue": "2", "pages": "L161-L164" }, { "id": "authors:njerz-qrq56", "collection": "authors", "collection_id": "njerz-qrq56", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20100223-132200164", "type": "article", "title": "Magnesium Isotopes in Metal-poor Dwarfs: The Rise of AGB Stars and the Formation Timescale of the Galactic Halo", "author": [ { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We have determined magnesium isotopic ratios (^(25, 26)Mg/Mg) in metal-poor (-2.6 \u2264 [Fe/H] \u2264 -1.3) halo dwarfs employing high signal-to-noise ratio (S/N = 90-280), high spectral resolution (R = 10^5) Keck High Resolution Echelle Spectrometer (HIRES) spectra. Unlike previous claims of an important contribution from intermediate-mass asymptotic giant branch (AGB) stars at low metallicities, we find that the rise of the AGB contribution in the Galactic halo did not occur until intermediate metallicities ([Fe/H] \u2273 -1.5).", "doi": "10.1086/516735", "issn": "2041-8205", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Letters", "publication_date": "2007-04-10", "series_number": "1", "volume": "659", "issue": "1", "pages": "L25-L28" }, { "id": "authors:y34ss-sdh52", "collection": "authors", "collection_id": "y34ss-sdh52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:COHaj07", "type": "article", "title": "Integrated-light Two Micron All Sky Survey infrared photometry of Galactic globular clusters", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Hsieh", "given_name": "Scott", "clpid": "Hsieh-Scott" }, { "family_name": "Metchev", "given_name": "Stanimir", "orcid": "0000-0003-3050-8203", "clpid": "Metchev-S" }, { "family_name": "Djorgovski", "given_name": "S. G.", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-S-G" }, { "family_name": "Malkan", "given_name": "M.", "orcid": "0000-0001-6919-1237", "clpid": "Malkan-M" } ], "abstract": "We have mosaicked Two Micron All Sky Survey (2MASS) images to derive surface brightness profiles in J, H, and K_s for 104 Galactic globular clusters. We fit these with King profiles and show that the core radii are identical to within the errors for each of these IR colors and are identical to the core radii at V in essentially all cases. We derive integrated-light colors V-J, V-H, V-K_s, J-H, and J-Ks for these globular clusters. Each color shows a reasonably tight relation between the dereddened colors and metallicity. Fits to these are given for each color. The IR-IR colors have very small errors, due largely to the all-sky photometric calibration of the 2MASS survey, while the V-IR colors have substantially larger uncertainties. We find fairly good agreement with measurements of integrated-light colors for a smaller sample of Galactic globular clusters by M. Aaronson, M. Malkan, and D. Kleinmann from 1977. Our results provide a calibration for the integrated light of distant single-burst old stellar populations from very low to solar metallicities. A comparison of our dereddened measured colors with predictions from several models of the integrated light of single-burst old populations shows good agreement in the low-metallicity domain for V-K_s colors but also shows an offset at a fixed [Fe/H] of ~0.1 mag in J-K_s, which we ascribe to photometric system transformation issues. Some of the models fail to reproduce the behavior of the integrated-light colors of the Galactic globular clusters near solar metallicity.", "doi": "10.1086/509127", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2007-01", "series_number": "1", "volume": "133", "issue": "1", "pages": "99-121" }, { "id": "authors:6sag2-qqb76", "collection": "authors", "collection_id": "6sag2-qqb76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:COHapjl06", "type": "article", "title": "The not so extraordinary globular cluster 037-B327 in M31", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "A velocity dispersion has been measured for the luminous globular cluster M31 037-B327, claimed to be the most massive star cluster in the Local Group and to be a young \"super star cluster\" that has survived to an old age. M31 037-B327 has a mass comparable to that of M31 G1 but not significantly larger. Although near the upper end for the mass distribution of globular clusters, it is not an unprecedented extraordinary object.", "doi": "10.1086/510384", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2006-12-10", "series_number": "1", "volume": "653", "issue": "1", "pages": "L21-L23" }, { "id": "authors:44bsa-dqn75", "collection": "authors", "collection_id": "44bsa-dqn75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190521-160258047", "type": "article", "title": "Carbon Stars in the Hamburg/ESO Survey: Abundances", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Shectman", "given_name": "Stephen", "clpid": "Shectman-S-A" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Ramirez", "given_name": "Solange", "clpid": "Ram\u00edrez-S-V" }, { "family_name": "Swensson", "given_name": "Amber", "clpid": "Swensson-A" }, { "family_name": "Zickgraf", "given_name": "Franz-Josef", "clpid": "Zickgraf-F-J" } ], "abstract": "We have carried out a detailed abundance analysis using high-dispersion spectra from HIRES at Keck for a sample of 16 carbon stars found among candidate extremely metal-poor (EMP) stars from the Hamburg/ESO Survey (HES). We find that the Fe metallicities for the cooler C stars (T_(eff) ~ 5100 K) have been underestimated by a factor of ~10 by the standard HES tools. The results presented here provided crucial supporting data used recently by Cohen et al. to derive the frequency of C stars among EMP stars. C enhancement in these EMP C stars appears to be independent of Fe metallicity and approximately constant at ~1/5 the solar \u03f5(C). The C enhancement shows some evidence of decreasing with decreasing T_(eff) (increasing luminosity), presumably due to mixing and dredge-up of C-depleted material. The mostly low ^(12)C/^(13)C ratios (~4) and the high N abundances in many of these stars suggest that material that has been through proton burning via the CN cycle comprises most of the stellar envelope. C enhancement in this sample is associated with strong enrichment of heavy nuclei beyond the Fe peak for 12 of the 16 stars. The remaining C stars from the HES, which tend to be the most Fe-poor, show no evidence for enhancement of the heavy elements. Very high enhancements of lead are detected in some of the C stars with highly enhanced Ba. The strong lead lines, the high Ba/Eu ratios, and the high ratios of abundances of the diagnostic elements in the first and second s-process peaks demonstrate that the s-process is responsible for the enhancement of the heavy elements for the majority of the C stars in our sample. The low ^(12)C/^(13)C ratios and large C and N enhancements of the EMP C stars are more extreme than those of intrinsic asymptotic giant branch C stars of near-solar Fe metallicity, but closer to the composition of CH stars. Our subsample of EMP C stars without s-process enhancement is reminiscent of the R-type C stars in the solar neighborhood; thus, we expect that they are formed by similar mechanisms. We suggest that both the s-process-enhanced and Ba-normal C stars result from phenomena associated with mass transfer in binary systems. This leads directly to the progression from C stars to CH stars and then to Ba stars as the Fe metallicity increases.", "doi": "10.1086/504597", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2006-07", "series_number": "1", "volume": "132", "issue": "1", "pages": "137-160" }, { "id": "authors:pfj7j-v5a65", "collection": "authors", "collection_id": "pfj7j-v5a65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110616-152103776", "type": "article", "title": "First Results on Shear-selected Clusters from the Deep Lens Survey: Optical Imaging, Spectroscopy, and X-Ray Follow-up", "author": [ { "family_name": "Wittman", "given_name": "D.", "orcid": "0000-0002-0813-5888", "clpid": "Wittman-D" }, { "family_name": "Dell'Antonio", "given_name": "I. P.", "clpid": "Dell'Antonio-I-P" }, { "family_name": "Hughes", "given_name": "J. P.", "clpid": "Hughes-J-P" }, { "family_name": "Margoniner", "given_name": "V. E.", "clpid": "Margoniner-V-E" }, { "family_name": "Tyson", "given_name": "J. A.", "clpid": "Tyson-J-A" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Norman", "given_name": "D.", "clpid": "Norman-D" } ], "abstract": "We present the first sample of galaxy clusters selected on the basis of their weak gravitational lensing shear. The shear induced by a cluster is a function of its mass profile and its redshift relative to the background galaxies being sheared; in contrast to more traditional methods of selecting clusters, shear selection does not depend on the cluster's star formation history, baryon content, or dynamical state. Because mass is the property of clusters that provides constraints on cosmological parameters, the dependence on these other parameters could induce potentially important biases in traditionally selected samples. Comparison of a shear-selected sample with optically and X-ray-selected samples is therefore of great importance. Here we present the first step toward a new shear-selected sample: the selection of cluster candidates from the first 8.6 deg^2 of the 20 deg^2 Deep Lens Survey (DLS), and tabulation of their basic properties such as redshifts and optical and X-ray counterparts.", "doi": "10.1086/502621", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2006-05-20", "series_number": "1", "volume": "643", "issue": "1", "pages": "128-143" }, { "id": "authors:mqwgb-ftq71", "collection": "authors", "collection_id": "mqwgb-ftq71", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110322-113752943", "type": "book_section", "title": "Chemical Abundance Inhomogeneities in Globular Cluster Stars", "book_title": "Chemical Abundances and Mixing in Stars in the Milky Way and its Satellites", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Randich", "given_name": "Sofia", "clpid": "Randich-S" }, { "family_name": "Pasquini", "given_name": "Luca", "clpid": "Pasquini-L" } ], "abstract": "It is now clear that abundance variations from star-to-star among the light elements, particularly C, N, O, Na and Al, are ubiquitous within galactic globular clusters; they appear seen whenever data of high quality is obtained for a sufficiently large sample of stars within such a cluster. The correlations and anti-correlations among these elements and the range of variation of each element appear to be independent of stellar evolutionary state, with the exception that enhanced depletion of C and of O is sometimes seen just at the RGB tip. While the latter behavior is almost certainly due to internal production and mixing, the internal mixing hypothesis can now be ruled out for producing the bulk of the variations seen. We focus on the implications of our new data for any explanation invoking primordial variations in the proto-cluster or accretion of polluted material from a neighboring AGB star.", "doi": "10.1007/978-3-540-34136-9_38", "isbn": "3-540-34135-8", "publisher": "Springer", "place_of_publication": "New York, NY", "publication_date": "2006", "pages": "103-106" }, { "id": "authors:7ww1s-qq786", "collection": "authors", "collection_id": "7ww1s-qq786", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-080900319", "type": "article", "title": "To Be or Not to Be: Very Young Globular Clusters in M31", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Matthews", "given_name": "Keith", "clpid": "Matthews-Keith-Astronomy" }, { "family_name": "Cameron", "given_name": "P. Brian", "clpid": "Cameron-P-B" } ], "abstract": "We present observations made with the newly commissioned Keck laser guide star adaptive optics (LGSAO) system of six objects in M31 that are alleged in multiple recent studies to be young globular clusters (GCs); all are supposed to have ages \u22645 Gyr. The resulting FWHM of the PSF core in our images is ~70 mas. The four youngest of these objects are asterisms; they are with certainty not young GCs in M31. Based on their morphology, the two oldest are GCs in M31. While the M31 GCs with ages 5-8 Gyr appear to be mostly genuine, it appears that many of the alleged very young GCs in M31 are spurious identifications. This problem will be even more severe in studies now underway of the GC systems of more distant spiral galaxies, for which imaging at the spatial resolution of our observations in M31 may not be adequate to detect sample contamination by asterisms.", "doi": "10.1086/498649", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2005-11-20", "series_number": "1", "volume": "634", "issue": "1", "pages": "L45-L48" }, { "id": "authors:vr1hm-phz21", "collection": "authors", "collection_id": "vr1hm-phz21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-080209202", "type": "article", "title": "Frequency of Carbon Stars among Extremely Metal-poor Stars", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Shectman", "given_name": "Stephen", "clpid": "Shectman-S-A" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Zickgraf", "given_name": "Franz-Josef", "clpid": "Zickgraf-F-J" }, { "family_name": "Ram\u00edrez", "given_name": "Solange", "clpid": "Ram\u00edrez-S-V" }, { "family_name": "Swenson", "given_name": "Amber", "clpid": "Swenson-A" } ], "abstract": "We demonstrate that there are systematic scale errors in the [Fe/H] values determined by the Hamburg/ESO Survey (HES; and by inference by the HK survey in the past) for certain extremely metal-poor, highly C-enhanced giants. The consequences of these scale errors are that (1) the fraction of carbon stars at extremely low metallicities has been overestimated in several papers in the recent literature, (2) the number of extremely metal-poor stars known is somewhat lower than has been quoted in the recent literature, and (3) the yield for extremely metal-poor stars by the HES is somewhat lower than is stated in the recent literature. A preliminary estimate for the frequency of carbon stars among the giants in the HES sample with -4 < [Fe/H] < -2.0 dex is 7.4% \u00b1 2.9%; adding an estimate for the C-enhanced giants with [C/Fe] > 1.0 dex without detectable C_2 bands raises the fraction to 14% \u00b1 4%. We rely on the results of an extensive set of homogeneous, detailed abundance analyses of stars expected to have [Fe/H] \u2264 -3.0 dex selected from the HES to establish these claims. We have found that the Fe metallicity of the cooler (T_(eff) \u227e 5200 K) C stars as derived from spectra taken with HIRES at Keck are a factor of ~10 higher than those obtained via the algorithm used by the HES project to analyze the moderate-resolution follow-up spectra, and this algorithm is identical to that used until very recently by the HK survey. This error in the Fe abundance estimate for C stars arises from a lowering of the emitted flux in the continuum bandpasses of the KP index (Ca II \u03bb3933) and, particularly, the HP2 (H\u03b4) index used to estimate [Fe/H] due to absorption from strong molecular bands.", "doi": "10.1086/498502", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2005-11-10", "series_number": "2", "volume": "633", "issue": "2", "pages": "L109-L112" }, { "id": "authors:yg52y-5jy42", "collection": "authors", "collection_id": "yg52y-5jy42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-104836583", "type": "article", "title": "C and N Abundances in Stars at the Base of the Red Giant Branch in M15", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Briley", "given_name": "Michael M.", "clpid": "Briley-M-M" }, { "family_name": "Stetson", "given_name": "Peter B.", "orcid": "0000-0001-6074-6830", "clpid": "Stetson-P-B" } ], "abstract": "We present an analysis of a large sample of moderate-resolution Keck Low Resolution Imaging Spectrometer spectra of subgiants and stars at the base of the red giant branch (RGB) in the Galactic globular cluster (GC) M15 (NGC 7078), most within the range 16.5 < V < 19.5 (1.2 < M_V < 4.2), with the goal of deriving C abundances (from the G band of CH) and N abundances (from the NH band at 3360 \u00c5). Star-to-star stochastic variations with significant range in both [C/Fe] and [N/Fe] are found at all luminosities extending to the subgiants at M_V ~ +3. The C and N abundances appear anticorrelated, as would be expected from the CN-cycle processing of stellar material. Yet these M15 stars are considerably fainter than the RGB bump, the point at which deep mixing is believed to set in. On this basis, while the observed abundance pattern is consistent with proton-capture nucleosynthesis, we infer that the site of the reactions is likely not within the present sample. The range of variation of the N abundances is very large, and the sum of C + N increases as C decreases. To reproduce this requires the incorporation not only of CN but also of ON-processed material. Combining our work with that of Trefzger and coworkers for the brighter giants in M15, we find strong evidence for additional depletion of C among the most luminous giants. This presumably represents the first dredge-up (with enhanced deep mixing) expected for such luminous cluster RGB stars in the course of normal stellar evolution as they cross the RGB bump.\nWe compare the behavior of these patterns for C and N in GCs covering a wide range of metallicity and current mass. While all clusters studied show strong anticorrelated variations of C and N at all luminosities probed, the metal-rich clusters (M71, 47 Tuc, and M5) do not show evidence for the first dredge-up among their most luminous giants, while the metal-poor ones (M13, M92, and M15, plus M5) do. Conversely, the metal-poor clusters do not show evidence for the bimodality in CH and CN line strengths seen in the metal-rich clusters. The collected data on C and N abundances in low-luminosity GC stars cannot be explained by the commonly invoked models for the chemical evolution of GC stars; in particular, \"pollution\" of existing low-mass stars by ejecta from intermediate-mass asymptotic giant branch (AGB) stars can be ruled out. Pollution of cluster gas by such stars prior to the formation of the lower mass stars we observe today can also be ruled out unless current models of nucleosynthesis and dredge-up into the surface layers of AGB stars are flawed; such models agree qualitatively but disagree quantitatively with our data. We are forced to assume that there was an extended period of star formation in GCs, and that a previous generation of more massive stars evolved, ejected mass, and polluted the GC gas with light elements; the low-mass stars we see today formed afterward. A tentative scenario is developed involving an initial phase of star formation heavily biased toward high-mass stars, with subsequent formation of intermediate-mass, then low-mass stars.", "doi": "10.1086/431974", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2005-09", "series_number": "3", "volume": "130", "issue": "3", "pages": "1177-1193" }, { "id": "authors:c1jd6-cy231", "collection": "authors", "collection_id": "c1jd6-cy231", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-112412308", "type": "article", "title": "Analysis of the carbon-rich very metal-poor dwarf G77\u201361", "author": [ { "family_name": "Plez", "given_name": "B.", "clpid": "Plez-B" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present an analysis of the carbon dwarf G77\u201361, a known binary, based on high resolution Keck spectra. G77\u201361 has a very-low metallicity, although not as extreme as what was previously conjectured. This star is very carbon-enhanced, the spectra showing very strong CH, CN, and C_2 bands of both ^(13)C and ^(12)C isotopes. Atomic lines are sparse, and often blended, but we were able to derive abundances for Na, Mg, Ca, Cr, Mn, and Fe. Its [Fe/H] of -4.03 \u00b1 0.1 places it among the lowest metallicity stars known, and its very high [C/Fe] = +2.6 , and [N/Fe] = +2.6 among the most C and N-rich metal-poor stars. The carbon isotopic ratio is ^(12)C/^(13)C = 5 \u00b1 1. No overabundance of s- or r-process elements is detectable, but the upper limits that can be set on these overabundances are not very constraining.", "doi": "10.1051/0004-6361:20042082", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy and Astrophysics", "publication_date": "2005-05-11", "series_number": "3", "volume": "434", "issue": "3", "pages": "1117-1124" }, { "id": "authors:vaatc-hgp54", "collection": "authors", "collection_id": "vaatc-hgp54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-103855423", "type": "book_section", "title": "The Frequency of Carbon Rich Stars Among Extremely Metal Poor Stars", "book_title": "From Lithium to Uranium: Elemental Tracers of Early Cosmic Evolution", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Shectman", "given_name": "Stephen", "clpid": "Shectman-S-A" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" }, { "family_name": "Zickgraf", "given_name": "Franz-Josef", "clpid": "Zickgraf-F-J" }, { "family_name": "Ramirez", "given_name": "Solange", "clpid": "Ram\u00edrez-S-V" }, { "family_name": "Swenson", "given_name": "Amber", "clpid": "Swenson-A" } ], "contributor": [ { "family_name": "Hill", "given_name": "V.", "clpid": "Hill-V" }, { "family_name": "Fran\u00e7ois", "given_name": "P.", "clpid": "Fran\u00e7ois-P" }, { "family_name": "Primas", "given_name": "F.", "clpid": "Primas-F" } ], "abstract": "We discuss the fraction of carbon stars (C-stars) and of C-enhanced stars among samples of candidate extremely metal poor (EMP: [Fe/H] \u2a7d\u22123.0 dex) stars selected from the Hamburg/ESO Survey (HES), obtaining a total for C-rich stars with [C/Fe] \u2a7e +1.0 dex of 14.4\u00b14%. We also present the key results of detailed abundance analyses of a sample of 14 C-stars selected in this way.", "doi": "10.1017/s1743921305005570", "isbn": "9780521851992", "publisher": "Cambridge University Press", "place_of_publication": "Cambridge", "publication_date": "2005-05", "pages": "213-218" }, { "id": "authors:dsgqh-vdm51", "collection": "authors", "collection_id": "dsgqh-vdm51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-081846297", "type": "article", "title": "Outer Versus Inner Halo Globular Clusters: NGC 7492 Abundances", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" } ], "abstract": "We have carried out a detailed abundance analysis for 21 elements in a sample of four RGB stars in the outer halo globular cluster NGC 7492 (R_(GC) 25 kpc); we find [Fe/H] = -1.82 dex inferred from Fe Ilines (-1.79 from Fe II) using high-dispersion (R = \u03bb/\u0394\u03bb = 35,000) spectra obtained with HIRES at the Keck Observatory. Most elements show no sign of star-to-star variation within our limited sample. We have, however, detected an anticorrelation between O and Na abundances similar to that seen in our previous analyses of inner halo GCs as well as in studies of relatively nearby GCs by others. We compare the abundance ratios in NGC 7492 with those we previously determined for the much closer old halo GCs M3 and M13. After making corrections for trends of abundance ratio with metallicity characteristic of halo stars, we find that for these three GCs, for each of the elements in common we deduce identical abundance ratios with respect to Fe to within the probable measurement uncertainties. Thus, the chemical history of the outer halo as exemplified by the metal-poor outer halo globular cluster NGC 7492 is indistinguishable from that of the inner halo, exemplified by M3 and M13, at least through the epoch of formation of these old globular clusters. This applies to the neutron capture processes as well.", "doi": "10.1086/427717", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2005-03", "series_number": "3", "volume": "129", "issue": "3", "pages": "1607-1615" }, { "id": "authors:hassb-93p91", "collection": "authors", "collection_id": "hassb-93p91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-082652543", "type": "article", "title": "Abundances in a Large Sample of Stars in M3 and M13", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Mel\u00e9ndez", "given_name": "Jorge", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" } ], "abstract": "We have carried out a detailed abundance analysis for 21 elements in a sample of 25 stars with a wide range in luminosity from luminous giants to stars near the main-sequence turnoff in the globular cluster M13 ([Fe/H] = -1.50 dex) and in a sample of 13 stars distributed from the tip to the base of the red giant branch (RGB) in the globular cluster M3 ([Fe/H] = -1.39 dex). The analyzed spectra, obtained with HIRES at the Keck Observatory, are of high dispersion (R = \u03bb/\u0394\u03bb = 35,000). Most elements, including Fe, show no trend with T_(eff) and low scatter around the mean between the top of the RGB and near the main-sequence turnoff, suggesting that at this metallicity, non-LTE effects and gravitationally induced heavy-element diffusion are not important for this set of elements over the range of stellar parameters spanned by our sample. We have detected an anticorrelation between O and Na abundances, observed previously among the most luminous RGB stars in both of these clusters, in both M3 and in M13 over the full range of luminosity of our samples, i.e., in the case of M13 to near the main-sequence turnoff. M13 shows a larger range in both O and Na abundance than does M3 at all luminosities, in particular having a few stars at its RGB tip with unusually strongly depleted O. We detect a correlation between Mg abundance and O abundance among the stars in the M13 sample. We also find a decrease in the mean Mg abundance as one moves toward lower luminosity, which we tentatively suggest is due to our ignoring non-LTE effects in Mg. Although CN burning must be occurring in both M3 and in M13, and ON burning is required for M13, we combine our new O abundances with published C and N abundances to confirm with quite high precision that the sum of C+N+O is constant near the tip of the giant branch, and we extend this down to the bump in the luminosity function. The same holds true for a smaller sample in M3, with somewhat larger variance. Star I-5 in M13 has large excesses of Y and of Ba, with no strong enhancement of Eu, suggesting that an s-process event contributed to its heavy-element abundances. The mean abundance ratios for M3 and for M13 are identical to within the errors. They show the typical pattern for metal-poor globular clusters of scatter among the light elements, with the odd atomic number elements appearing in the mean enhanced. The Fe-peak elements, where the odd atomic number elements are excessively depleted, do not show any detectable star-to-star variations in either cluster. The abundance ratios for 13 Galactic globular clusters with recent detailed abundance analyses, obtained by combining our samples with published data, are compared with those of published large surveys of metal-poor halo field stars. For most elements, the agreement is very good, suggesting a common chemical history for the halo field and cluster stars.", "doi": "10.1086/426369", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2005-01", "series_number": "1", "volume": "129", "issue": "1", "pages": "303-329" }, { "id": "authors:wjaqf-26f12", "collection": "authors", "collection_id": "wjaqf-26f12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190607-161647635", "type": "publication_whitepaper", "title": "Extremely Metal-Poor Stars: The Local High Redshift Universe", "author": [ { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Beers", "given_name": "Timothy C.", "orcid": "0000-0003-4573-6233", "clpid": "Beers-T-C" }, { "family_name": "Frebel", "given_name": "Anna", "orcid": "0000-0002-2139-7145", "clpid": "Frebel-A" }, { "family_name": "Johnson", "given_name": "Jennifer", "clpid": "Johnson-J" }, { "family_name": "Lai", "given_name": "David", "clpid": "Lai-David" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Rockosi", "given_name": "Constance", "clpid": "Rockosi-C-M" }, { "family_name": "Shectman", "given_name": "Stephen", "clpid": "Shectman-S-A" }, { "family_name": "Sneden", "given_name": "Christopher", "orcid": "0000-0002-3456-5929", "clpid": "Sneden-C" } ], "abstract": "Extremely metal-poor (EMP) stars can only have formed early in the history of the Galaxy, and\nrepresent the local equivalent of the high redshift universe. With them, we can study the early\nsupernovae, the early chemical evolution of the Galaxy, and the history of star formation in the\nMilky Way. By analogy we can learn about those epochs of galaxy formation in the distant past\nthat are currently at such high redshifts that they are beyond the reach of even the largest existing\ntelescopes, a technique some call \"near-field cosmology\".\nWhile H, He, and some Li came out of the Big Bang, all other elements were formed in stars,\nand were dispersed by supernovae and stellar winds into the gas from which subsequent stellar\ngenerations formed. The ejecta from supernovae played the most important role in the early\nUniverse. SN models have many parameters, including the history of the progenitor star (initial\nmass, mass loss history, internal nucleosynthesis history prior to the explosion, etc), the details of\nthe explosion (energy, ejected mass, mixing) etc. There are vigorous groups pursuing the details of\nthese models both theoretically and computationally in the US and abroad. But there are so many\nfree or poorly known parameters that these efforts are best guided by observations of metal-poor\nstars.", "publisher": "Caltech Library", "publication_date": "2005" }, { "id": "authors:j5sk8-bry44", "collection": "authors", "collection_id": "j5sk8-bry44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190604-144843481", "type": "article", "title": "John Beverley Oke", "author": [ { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "John Beverley Oke, emeritus professor of astronomy at Caltech, died on 2 March 2004 of heart failure at his home in Victoria, British Columbia.", "doi": "10.1063/1.1878349", "issn": "0031-9228", "publisher": "American Institute of Physics", "publication": "Physics Today", "publication_date": "2004-12", "series_number": "12", "volume": "57", "issue": "12", "pages": "81-82" }, { "id": "authors:xtjf3-xhk48", "collection": "authors", "collection_id": "xtjf3-xhk48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-083404445", "type": "article", "title": "Abundances In Very Metal-Poor Dwarf Stars", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "McWilliam", "given_name": "Andrew", "clpid": "McWilliam-A" }, { "family_name": "Shectman", "given_name": "Steve", "clpid": "Shectman-S" }, { "family_name": "Thompson", "given_name": "Ian", "clpid": "Thompson-I" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" }, { "family_name": "Ivans", "given_name": "Inese", "clpid": "Ivans-I" }, { "family_name": "Dehn", "given_name": "Matthias", "clpid": "Dehn-M" }, { "family_name": "Karlsson", "given_name": "Torgny", "clpid": "Karlsson-T" }, { "family_name": "Mel\u00e9ndez", "given_name": "J.", "orcid": "0000-0002-4933-2239", "clpid": "Mel\u00e9ndez-J" } ], "abstract": "We discuss the detailed composition of 28 extremely metal-poor (EMP) dwarfs, 22 of which are from the Hamburg/ESO Survey (HES), based on Keck echelle spectra. Our sample has a median [Fe/H] of -2.7 dex, extends to -3.5 dex, and is somewhat less metal-poor than was expected from [Fe/H](HK, HES) determined from low-resolution spectra. Our analysis supports the existence of a sharp decline in the distribution of halo stars with metallicity below [Fe/H] = -3.0 dex. So far no additional turnoff stars with [Fe/H] < -3.5 have been identified in our follow-up efforts. For the best-observed elements between Mg and Ni, we find that the abundance ratios appear to have reached a plateau, i.e., [X/Fe] is approximately constant as a function of [Fe/H], except for Cr, Mn, and Co, which show trends of abundance ratios varying with [Fe/H]. These abundance ratios at low metallicity correspond approximately to the yield expected from Type II supernovae (SNe) with a narrow range in mass and explosion parameters; high-mass Type II SN progenitors are required. The dispersion of [X/Fe] about this plateau level is surprisingly small and is still dominated by measurement errors rather than intrinsic scatter. These results place strong constraints on the characteristics of the contributing SNe. The dispersion in neutron-capture elements and the abundance trends for Cr, Mn, and Co are consistent with previous studies of evolved EMP stars. We find halo-like enhancements for the \u03b1-elements Mg, Ca, and Ti, but solar Si/Fe ratios for these dwarfs. This contrasts with studies of EMP giant stars, which show Si enhancements similar to other \u03b1-elements. Sc/Fe is another case where the results from EMP dwarfs and from EMP giants disagree; our Sc/Fe ratios are enhanced compared to the solar value by ~0.2 dex. Although this conflicts with the solar Sc/Fe values seen in EMP giants, we note that \u03b1-like Sc/Fe ratios have been claimed for dwarfs at higher metallicity. Two dwarfs in the sample are carbon stars, while two others have significant C enhancements, all with ^(12)C/^(13)C ~7 and with C/N between 10 and 150. Three of these C-rich stars have large enhancements of the heavy neutron capture elements, including lead, which implies a strong s-process contribution, presumably from binary mass transfer; the fourth shows no excess of Sr or Ba.", "doi": "10.1086/422576", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2004-09-10", "series_number": "2", "volume": "612", "issue": "2", "pages": "1107-1135" }, { "id": "authors:fm8t1-r9w07", "collection": "authors", "collection_id": "fm8t1-r9w07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-084409685", "type": "article", "title": "The Chemical Inhomogeneity of Faint M13 Stars: Carbon and Nitrogen Abundances", "author": [ { "family_name": "Briley", "given_name": "Michael M.", "clpid": "Briley-M-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Stetson", "given_name": "Peter B.", "orcid": "0000-0001-6074-6830", "clpid": "Stetson-P-B" } ], "abstract": "Building upon earlier observations that demonstrate substantial star-to-star differences in the carbon abundances of M13 subgiants, we present new Keck LRIS spectra reaching more that 1.5 mag below the M13 main-sequence turnoff (to V \u2248 20). Our analysis reveals a distribution of C abundances similar to that found among the subgiants, implying little change in the compositions of the M13 stars at least through the main-sequence turnoff. We presume these differences to be the result of some process operating early in the cluster history. Additional spectra of previously studied bright M13 giants have been obtained with the 5 m Hale Telescope. A comparison of C abundances derived using the present methods and those from the literature yield a mean difference of 0.03 \u00b1 0.14 dex for four stars in common with the 1996 study by Smith et al. and 0.14 \u00b1 0.07 dex for stars also observed in Suntzeff's 1981 survey (if one extreme case is removed). We conclude that the lower surface C abundances of these luminous giants as compared with the subgiants and main-sequence stars are likely the result of mixing rather than a difference in our abundance scales. NH band strengths have also been measured for a handful of the most luminous M13 turnoff stars. While molecular band formation in such stars is weak, significant star-to-star NH band strength differences are present. Moreover, for the stars with both C and N measurements, differences between stars in these two elements appear to be anticorrelated. Finally, the most recent C and N abundances for main-sequence, main-sequence turnoff, and subgiant stars in 47 Tuc, M71, M5, and the present M13 data are compared.", "doi": "10.1086/382100", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2004-03", "series_number": "3", "volume": "127", "issue": "3", "pages": "1579-1587" }, { "id": "authors:75b0j-d6227", "collection": "authors", "collection_id": "75b0j-d6227", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190604-144843374", "type": "article", "title": "Palomar 12 as a Part of the Sagittarius Stream: The Evidence from Abundance Ratios", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present a detailed abundance analysis for 21 elements based on high-dispersion, high spectral resolution Keck spectra for four members of the outer halo \"young\" Galactic globular cluster Palomar 12. All four stars show identical abundance distributions with no credible indication of any star-to-star scatter. However, the abundance ratios of the Pal 12 stars are very peculiar. There is no detected enhancement of the \u03b1-elements; the mean of [Si/Fe], [Ca/Fe], and [Ti/Fe] is -0.07 \u00b1 0.05 dex, O/Fe is also solar, while Na is very deficient. The distribution among the heavy elements shows anomalies as well. These are inconsistent with those of almost all Galactic globular clusters or of field stars in the Galaxy. The peculiarities shown by the Pal 12 stars are, however, in good general agreement with the trends established by Smecker-Hane & McWilliam and by Bonifacio et al. for stars in the Sagittarius dwarf spheroidal (dSph) galaxy evaluated at the [Fe/H] of Pal 12. This reinforces earlier suggestions that Pal 12 originally was a cluster in the Sgr dSph galaxy that during the process of accretion of this galaxy by our own was tidally stripped from the Sgr galaxy to become part of the extended Sgr stream.", "doi": "10.1086/382104", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2004-03", "series_number": "3", "volume": "127", "issue": "3", "pages": "1545-1554" }, { "id": "authors:90m1g-j6a70", "collection": "authors", "collection_id": "90m1g-j6a70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103833520", "type": "article", "title": "Star Formation and X\u2010Ray Emission in Distant Star\u2010Forming Galaxies", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "About 45% of the point sources detected in the 2 Ms Chandra exposure of the Hubble Deep Field-North (HDF-N) can be matched with moderately bright galaxies with z < 1.4 that have been studied by the Caltech Faint Galaxy Redshift Survey. Although the optical spectra of these galaxies appear normal, based on their X-ray properties ~20% of them appear to contain weak active galactic nuclei (AGNs). More than 90% of the X-ray photons detected by Chandra from galaxies within the redshift regime 0.4 < z < 1.1 are powered by accretion onto massive black holes. For the sample of galaxies in common, we use their emitted luminosity in the 3727 \u00c5 line of [O II] to estimate their star formation rates (SFRs). The X-ray-emitting galaxies are not those with the highest rest-frame equivalent width in this emission line, but rather are among those with the highest SFRs. With SFRs corrected for inclination effects, the distant galaxies show an LX-SFR relationship that is comparable to that of local galaxies. The HDF sample has a significantly higher median SFR and median SFR/galaxy stellar mass than does a sample of local star-forming galaxies. We demonstrate that the observed SFR for most of the galaxies at z ~ 1 in the HDF sample, if maintained as constant over their ages, suffices to produce the stellar mass observed in these galaxies. A rise in SFR at still earlier times is not required. We provide further evidence to support the conclusion that, once AGNs are eliminated, X-ray emission in these distant star-forming galaxies is related to the SFR through the same physical mechanisms that prevail locally.", "doi": "10.1086/378764", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2003-11-20", "series_number": "1", "volume": "598", "issue": "1", "pages": "288-300" }, { "id": "authors:6x922-0dn23", "collection": "authors", "collection_id": "6x922-0dn23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-101040686", "type": "article", "title": "Weak\u2010Lensing Discovery and Tomography of a Cluster at z = 0.68", "author": [ { "family_name": "Wittman", "given_name": "D.", "orcid": "0000-0002-0813-5888", "clpid": "Wittman-D" }, { "family_name": "Margoniner", "given_name": "V. E.", "clpid": "Margoniner-V-E" }, { "family_name": "Tyson", "given_name": "J. A.", "clpid": "Tyson-J-A" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Becker", "given_name": "A. C.", "clpid": "Becker-A-C" }, { "family_name": "Dell'Antonio", "given_name": "I. P.", "clpid": "Dell'Antonio-I-P" } ], "abstract": "We report the weak-lensing discovery, spectroscopic confirmation, and weak-lensing tomography of a massive cluster of galaxies at z = 0.68, demonstrating that shear selection of clusters works at redshifts high enough to be cosmologically interesting. The mass estimate from weak lensing, 11.1 \u00b1 2.8 \u00d7 10^(14) (r/Mpc) M\u2609 within projected radius r, agrees with that derived from the spectroscopy (\u03c3_v= 980 km s^(-1)) and with the position of an arc that is likely to be a strongly lensed background galaxy. The redshift estimate from weak-lensing tomography is consistent with the spectroscopy, demonstrating the feasibility of baryon-unbiased mass surveys. This tomographic technique will be able to roughly identify the redshifts of any dark clusters that may appear in shear-selected samples up to z ~ 1.", "doi": "10.1086/378344", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2003-11-01", "series_number": "1", "volume": "597", "issue": "1", "pages": "218-224" }, { "id": "authors:4pe6w-3j818", "collection": "authors", "collection_id": "4pe6w-3j818", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161904291", "type": "book_section", "title": "A Progress Report on the Caltech Faint Galaxy Redshift Survey", "book_title": "Deep Fields", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Cristiani", "given_name": "Stefano", "clpid": "Cristiani-S" }, { "family_name": "Renzini", "given_name": "Alvio", "clpid": "Renzini-A" }, { "family_name": "Williams", "given_name": "Robert E.", "clpid": "Williams-R-E" } ], "abstract": "I review recent progress on determining the SEDs and luminosity functions for galaxies in the large magnitude limited sample in the region of the HDF-North of the Caltech Faint Galaxy Redshift Survey.", "doi": "10.1007/10854354_10", "isbn": "3540427996", "publisher": "Springer-Verlag", "place_of_publication": "Berlin", "publication_date": "2003-09-26", "pages": "49-53" }, { "id": "authors:3xqtw-y7g09", "collection": "authors", "collection_id": "3xqtw-y7g09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-085036264", "type": "article", "title": "The Ages and Abundances of a Sample of Globular Clusters in M49 (NGC 4472)", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blakeslee", "given_name": "J. P.", "clpid": "Blakeslee-J-P" }, { "family_name": "C\u00f4t\u00e9", "given_name": "P.", "orcid": "0000-0003-1184-8114", "clpid": "C\u00f4t\u00e9-P" } ], "abstract": "We present a study of the metallicity and age of the globular clusters system of M49 (NGC 4472), the most luminous galaxy in the Virgo Cluster. We measure Lick indices for 47 globular clusters (GCs) in M49 from LRIS/Keck spectra and establish their metallicity parameters qualitatively in comparison to the Galactic GCs and to published data for 150 M87 GCs. We then compare our measurements with the predictions of models for the integrated light of old single-burst stellar systems by Worthey and by Thomas, Maraston, & Bender. We find that the metallicity of the M49 GC system spans the range from [Fe/H]_Z = -2.0 to +0.4 dex. We show that the metallicity and age parameters for these two GC systems are basically identical, except that the M49 GCs reach slightly higher metallicities than do those of M87. We find that the GCs of both of these giant elliptical galaxies are \u03b1-enhanced by a factor of about 2 above the solar value, as is also true of the Galactic GCs. Thus the most metal rich GCs in M49 reach [Z/H] ~ +0.8 dex, comparable to that of M49 itself. While adoption of the \u03b1-enhanced models of Thomas et al. has eliminated most of the previous discrepancies with observations, the most metal rich M49 GCs have Na D lines that are still considerably stronger than those predicted by any model, and there are still issues involving the metallicity scale of these models. We find that in the mean, the M49 GCs are at least 10 Gyr old. However, the grids of models we used differ in how they treat the horizontal branch, and this perceptibly affects the predicted H\u03b2 index. Hence our current incomplete understanding of the role of the horizontal branch limits our ability to derive a more detailed distribution for the ages of the GCs in M49 and in M87.", "doi": "10.1086/375865", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2003-08-01", "series_number": "2", "volume": "592", "issue": "2", "pages": "866-883" }, { "id": "authors:4501t-n0h93", "collection": "authors", "collection_id": "4501t-n0h93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-085848832", "type": "article", "title": "Dynamics of the Globular Cluster System Associated with M49 (NGC 4472): Cluster Orbital Properties and the Distribution of Dark Matter", "author": [ { "family_name": "C\u00f4t\u00e9", "given_name": "Patrick", "orcid": "0000-0003-1184-8114", "clpid": "C\u00f4t\u00e9-P" }, { "family_name": "McLaughlin", "given_name": "Dean E.", "clpid": "McLaughlin-D-E" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blakeslee", "given_name": "John P.", "clpid": "Blakeslee-J-P" } ], "abstract": "Using the Low Resolution Imaging Spectrometer on the Keck I and II telescopes, we have measured radial velocities for 196 globular clusters (GCs) around M49 (NGC 4472), the brightest member of the Virgo Cluster. Combined with published data, they bring the total number of GCs with measured radial velocities in this galaxy to 263. In terms of sample size, spatial coverage, velocity precision, and the availability of metallicity estimates from Washington photometry, this radial velocity database resembles that presented recently for M87 (NGC 4486), Virgo's cD galaxy and its second-ranked member. We extract the projected kinematics of the full sample of GCs and of separate subsamples of 158 metal-poor and 105 metal-rich GCs. In agreement with previous results for the global GC kinematics based on smaller data sets, we find that the GC system as a whole exhibits a slow overall rotation that is due almost entirely to a net rotation of the metal-poor GC subsystem alone. In a spatial average, the metal-rich GCs show essentially no rotation. As a function of galactocentric position, the metal-poor GCs rotate roughly about the photometric minor axis of M49 and at an approximately constant level of \u03a9R ~ 100-150 km s^(-1) out to R \u2243 2R_(eff). The metal-rich GC system shows some evidence (at roughly 1 \u03c3 significance) for weak rotation (\u03a9R ~ 50 km s^(-1)) beyond R \u22730.5R_(eff), also about the galaxy's minor axis, but in the opposite direction from the metal-poor GCs. Outside of R ~ R_(eff), the line-of-sight velocity dispersion of the metal-poor GCs exceeds that of their metal-rich counterparts by ~50%. We also note the presence of a well-defined grouping of 10 metal-rich GCs that are located at opposite poles along the galaxy's major axis and that appear to be rotating at nearly 300 km s-1 about the minor axis. This grouping may be the relic of a past merger or accretion event. The dynamics of the GC system is modeled by using published catalogs and number counts to define three-dimensional GC density distributions as input to a Jeans equation analysis. We show that the GC radial velocities alone point unequivocally, and independently of X-ray observations, to the need for a massive dark halo associated with M49 and the Virgo B subcluster around it. We then use a mass model for M49/Virgo B, constructed without reference to any GC data and described in detail in a forthcoming paper, to infer the orbital properties of the M49 globulars. The GC system as a whole is shown to be consistent with an almost perfectly isotropic velocity ellipsoid.It is more difficult to draw any firm conclusions on the orbital (an)isotropy of the two metallicity subsamples, as a result of the large uncertainties in their individual spatial density profiles and the poorly observationally defined kinematics of the metal-rich GCs in particular. After M87, M49 is the second elliptical galaxy for which we have been able to demonstrate velocity isotropy in the GC system overall, when no division based on GC color or metallicity is attempted. Thus, the data for these two galaxies lend support to the general assumption of isotropy when using GC kinematics to study the dark matter distribution in early-type galaxies. We also compare the kinematic properties of the GC system of M49 to those of M87, M31, and the Milky Way, the other galaxies for which samples of 100 or more GC velocities have been accumulated. We argue that, contrary to the traditional view of GCs as nonrotating, or slowly rotating, systems, rotation may in fact be a common by-product of the formation of GC systems. However, the quantitative details of the rotation are still not clear, particularly with regard to the question of possible differences between metal-poor and metal-rich globulars.", "doi": "10.1086/375488", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2003-07-10", "series_number": "2", "volume": "591", "issue": "2", "pages": "850-877" }, { "id": "authors:fphrw-mw944", "collection": "authors", "collection_id": "fphrw-mw944", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20131210-145233709", "type": "article", "title": "Abundance Analysis of HE 2148\u20131247, A Star with Extremely Enhanced Neutron Capture Elements", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Qian", "given_name": "Y.-Z.", "clpid": "Qian-Y-Z" }, { "family_name": "Wasserburg", "given_name": "G. J.", "orcid": "0000-0002-7957-8029", "clpid": "Wasserburg-G-J" } ], "abstract": "Abundances for 27 elements in the very metal-poor dwarf star HE 2148-1247 are presented, including many of the neutron capture elements. We establish that HE 2148-1247 is a very highly s-process-enhanced star with anomalously high Eu as well, Eu/H ~ half-solar, demonstrating the large addition of heavy nuclei at [Fe/H] = -2.3 dex. Ba and La are enhanced by a somewhat larger factor and reach the solar abundance, while Pb significantly exceeds it, thus demonstrating the addition of substantial s-process material. Ba/Eu is 10 times the solar r-process ratio but much less than that of the s-process, indicating a substantial r-process addition as well. C and N are also very highly enhanced. We have found that HE 2148-1247 is a radial velocity variable; it is probably a small-amplitude long-period binary. The C, N, and the s-process element enhancements were thus presumably produced through mass transfer from a former asymptotic giant branch (AGB) binary companion. The large enhancement of heavy r-nuclides also requires an additional source as this is far above any inventory in the interstellar medium at such low [Fe/H]. We consider that the s-process material was added by mass transfer of a more massive companion during its thermally pulsating AGB phase and ending up as a white dwarf. We further hypothesize that accretion onto the white dwarf from the envelope of the star caused accretion-induced collapse of the white dwarf, forming a neutron star, which then produced heavy r-nuclides and again contaminated its companion. This mechanism in a binary system can thus enhance the envelope of the lower mass star in s- and r-process material sequentially. Through analysis of the neutron capture element abundances taken from the literature for a large sample of very metal-poor stars, we demonstrate, as exemplified by HE 2148-1247, that mass transfer in a suitable binary can be very efficient in enhancing the heavy elements in a star; it appears to be capable of enhancing the s-process elements in very metal-poor stars to near the solar abundance but not substantially above it. The yield of Pb relative to Ba appears to vary among very metal-poor stars.", "doi": "10.1086/374269", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2003-05-10", "series_number": "2", "volume": "588", "issue": "2", "pages": "1082-1098" }, { "id": "authors:cg2cy-7vz96", "collection": "authors", "collection_id": "cg2cy-7vz96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-090806413", "type": "article", "title": "Stellar Archaeology: A Keck Pilot Program on Extremely Metal-Poor Stars From the Hamburg/ESO Survey. III. The Lead (P[CLC]b[/CLC]) Star HE 0024\u22122523", "author": [ { "family_name": "Lucatello", "given_name": "Sara", "clpid": "Lucatello-S" }, { "family_name": "Gratton", "given_name": "Raffaele", "clpid": "Gratton-R" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Beers", "given_name": "Timothy C.", "orcid": "0000-0003-4573-6233", "clpid": "Beers-T-C" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Carretta", "given_name": "Eugenio", "clpid": "Carretta-E" }, { "family_name": "Ram\u00edrez", "given_name": "Solange", "clpid": "Ram\u00edrez-S-V" } ], "abstract": "We present a detailed abundance analysis, including spectral syntheses, of a very metal-poor ([Fe/H] \u2243 -2.7) peculiar main-sequence star (HE 0024-2523) detected during the course of the Keck Pilot Program. Radial velocities of this star were obtained during four different observing runs over a time span of 1.1 yr and demonstrate that it is clearly a short-period spectroscopic binary. An orbital solution was obtained, and orbital parameters were determined with high precision. The rotational velocity was also measured (v_(rot) sin i = 9.7 \u00b1 1.5 km s^(-1)); rotation appears likely to be synchronous with the orbit. The abundance analysis and spectral syntheses indicate that the object is a CH star characterized by extreme s-process enrichment, likely due to mass accretion from an evolved companion that has now probably become a white dwarf. The lead (Pb) abundance of (HE 0024-2523) is very high, the same as that of the recently discovered lead-rich, metal-poor star CS 29526-110, [Pb/Fe] = +3.3. The abundance ratio of the heavy to light s-elements, as characterized by Pb and Ba, [Pb/Ba] = +1.9, is the highest yet found for any metal-poor star and is about 0.7 dex higher than that of CS 29526-110. On the basis of the measured isotopic ratio of carbon (C^(12)/C^(13) ~ 6) we argue that the mass donor must have had an original mass of at least ~3 M\u2299. The unusually short period of this CH star suggests that it underwent a past common-envelope phase with its evolved companion. Our results are compared with the latest available models for asymptotic giant branch yields and s-process nucleosynthesis. We also discuss the possible connection between HE 0024-2523, the lithium depletion of halo stars, and halo blue straggler formation.", "doi": "10.1086/345886", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2003-02", "series_number": "2", "volume": "125", "issue": "2", "pages": "875-893" }, { "id": "authors:ktevm-kg811", "collection": "authors", "collection_id": "ktevm-kg811", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-103246441", "type": "article", "title": "The Redshift of the Lensed Object in the Einstein Ring B0218+357", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Lawrence", "given_name": "Charles R.", "clpid": "Lawrence-C-R" }, { "family_name": "Blandford", "given_name": "Roger D.", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" } ], "abstract": "We present a secure redshift of z = 0.944 \u00b1 0.002 for the lensed object in the Einstein ring gravitational lens B0218+357 based on five broad emission lines, in good agreement with our preliminary value announced several years ago based solely on the detection of a single emission line.", "doi": "10.1086/344837", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2003-01-20", "series_number": "1", "volume": "583", "issue": "1", "pages": "67-69" }, { "id": "authors:gh2nb-mvw45", "collection": "authors", "collection_id": "gh2nb-mvw45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-075405923", "type": "article", "title": "Abundances in Stars from the Red Giant Branch Tip to near the Main-Sequence Turnoff in M5", "author": [ { "family_name": "Ram\u00edrez", "given_name": "Solange V.", "clpid": "Ram\u00edrez-S-V" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present the iron abundance and abundance ratios for 18 elements with respect to Fe in a sample of stars with a wide range in luminosity, from luminous giants to stars near the turnoff in the globular cluster M5. The analyzed spectra, obtained with the High Resolution Echelle Spectrograph at the Keck Observatory, are of high dispersion (R = \u03bb/\u0394\u03bb = 35,000). We find that the neutron capture, the iron peak, and the \u03b1-element abundance ratios show no trend with T_(eff) and low scatter around the mean between the top of the red giant branch and near the main-sequence turnoff, suggesting that at this metallicity non-LTE effects are not important over the range of stellar parameters spanned by our sample. To within the precision of the measurements (about \u00b10.1 dex), gravitationally induced heavy-element diffusion does not appear to be present among the stars near the main-sequence turnoff studied here. Our work and other recent studies suggest that heavy-element diffusion is inhibited in the surface layers of metal-poor stars. Differences in the Na abundance from star to star that extend to the main-sequence turnoff are detected in our sample in M5. The anticorrelation between O and Na abundances, observed in other metal-poor globular clusters, is not detected in our sample, but it may be hidden among stars with only upper limits for their O abundances. As we found in M71, there is a hint of star-to-star variation in the Zr abundance. Overall the abundance ratios of M5 appear very similar to those of M71, with the possible exception of the neutron capture element Ba, for which we argue that the apparent difference may be due to difficulties in the analysis. As in M71, the \u03b1-elements Mg, Ca, Si, and Ti are overabundant relative to Fe. The results of our abundance analysis of 25 stars in M5 provide further evidence of abundance variations among specific light elements at unexpectedly low luminosities, which cannot be explained by our current understanding of stellar evolution.", "doi": "10.1086/345510", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2003-01", "series_number": "1", "volume": "125", "issue": "1", "pages": "224-245" }, { "id": "authors:q5t33-g4t94", "collection": "authors", "collection_id": "q5t33-g4t94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-081435717", "type": "book_section", "title": "Star Formation in the Hubble Deep Field North", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Avila-Reese", "given_name": "Vladimir", "clpid": "Avila-Reese-V" }, { "family_name": "Firmani", "given_name": "Claudio", "clpid": "Firmani-C" }, { "family_name": "Frenk", "given_name": "Carlos S.", "clpid": "Frenk-C-S" }, { "family_name": "Allen", "given_name": "Christine", "clpid": "Allen-C" } ], "abstract": "I am currently analyzing the emission line spectra of the 600 galaxies from the sample of Cohen et al. (2000) and Cohen (2001) in the region of the HDF-North with z < 1.5. A progress report on this effort of the Caltech Faint Galaxy Redshift Survey is presented.", "doi": "10.48550/arXiv.0207298", "publisher": "Universidad Nacional Aut\u00f3noma de M\u00e9xico", "publication_date": "2003" }, { "id": "authors:mqdak-r1x87", "collection": "authors", "collection_id": "mqdak-r1x87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181213-143633825", "type": "book_section", "title": "Deep lens survey", "book_title": "Survey and Other Telescope Technologies and Discoveries", "author": [ { "family_name": "Wittman", "given_name": "D.", "clpid": "Wittman-D-M" }, { "family_name": "Tyson", "given_name": "J. A.", "clpid": "Tyson-J-A" }, { "family_name": "Dell'Antonio", "given_name": "I. P.", "clpid": "Dell'Antonio-I-P" }, { "family_name": "Becker", "given_name": "A. C.", "clpid": "Becker-A-C" }, { "family_name": "Margoniner", "given_name": "V. E.", "clpid": "Margoniner-V-E" }, { "family_name": "Cohen", "given_name": "J.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Norman", "given_name": "D.", "clpid": "Norman-D" }, { "family_name": "Loomba", "given_name": "D,", "clpid": "Loomba-D" }, { "family_name": "Squires", "given_name": "G.", "orcid": "0000-0002-1977-5717", "clpid": "Squires-G-K" }, { "family_name": "Wilson", "given_name": "G.", "orcid": "0000-0002-6572-7089", "clpid": "Wilson-G" }, { "family_name": "Stubbs", "given_name": "C.", "orcid": "0000-0003-0347-1724", "clpid": "Stubbs-C-W" }, { "family_name": "Hennawi", "given_name": "J.", "orcid": "0000-0002-7054-4332", "clpid": "Hennawi-J-F" }, { "family_name": "Spergel", "given_name": "D.", "orcid": "0000-0002-5151-0006", "clpid": "Spergel-D-N" }, { "family_name": "Boeshaar", "given_name": "P.", "clpid": "Boeshaar-P" }, { "family_name": "Clocchiatti", "given_name": "A.", "clpid": "Clocchiatti-A" }, { "family_name": "Hamuy", "given_name": "M.", "clpid": "Hamuy-M" }, { "family_name": "Bernstein", "given_name": "G.", "clpid": "Bernstein-G-M" }, { "family_name": "Gonzalez", "given_name": "A.", "orcid": "0000-0002-0933-8601", "clpid": "Gonzalez-A-H" }, { "family_name": "Guhathakurta", "given_name": "P.", "orcid": "0000-0001-8867-4234", "clpid": "Guhathakurta-P" }, { "family_name": "Hu", "given_name": "W.", "clpid": "Hu-W" }, { "family_name": "Seljak", "given_name": "U.", "clpid": "Seljak-U" }, { "family_name": "Zaritsky", "given_name": "D.", "orcid": "0000-0002-5177-727X", "clpid": "Zaritsky-D" } ], "contributor": [ { "family_name": "Tyson", "given_name": "J. Anthony", "clpid": "Tyson-J-A" }, { "family_name": "Wolff", "given_name": "Sidney", "clpid": "Wolff-S" } ], "abstract": "The Deep Lens Survey (DLS) is a deep BV Rz' imaging survey of seven 2\u00b0\u00d72\u00b0 degree fields, with all data to be made public. The primary scientific driver is weak gravitational lensing, but the survey is also designed to enable a wide array of other astrophysical investigations. A unique feature of this survey is the search for transient phenomena. We subtract multiple exposures of a field, detect differences, classify, and release transients on the Web within about an hour of observation. Here we summarize the scientific goals of the DLS, field and filter selection, observing techniques and current status, data reduction, data products and release, and transient detections. Finally, we discuss some lessons which might apply to future large surveys such as LSST.", "doi": "10.1117/12.457348", "isbn": "9780819446152", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "2002-12-24", "pages": "73-82" }, { "id": "authors:k2aje-3dv77", "collection": "authors", "collection_id": "k2aje-3dv77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181213-143633978", "type": "book_section", "title": "Imaging mass in three dimensions", "book_title": "Survey and Other Telescope Technologies and Discoveries", "author": [ { "family_name": "Wittman", "given_name": "D.", "clpid": "Wittman-D-E" }, { "family_name": "Margoniner", "given_name": "V. E.", "clpid": "Margoniner-V-E" }, { "family_name": "Tyson", "given_name": "J. A.", "clpid": "Tyson-J-A" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Becker", "given_name": "A. C.", "clpid": "Becker-A-C" }, { "family_name": "Dell'Antonio", "given_name": "I. P.", "clpid": "Dell'Antonio-I-P" } ], "contributor": [ { "family_name": "Tyson", "given_name": "J. Anthony", "clpid": "Tyson-J-A" }, { "family_name": "Wolff", "given_name": "Sidney", "clpid": "Wolff-S" } ], "abstract": "We explore a possible \"killer app\" for the LSST and similar surveys: imaging mass in three dimensions. We describe its scientific importance, practical techniques for realizing it, the current state of the art and how it might scale to the LSST.", "doi": "10.1117/12.457372", "isbn": "9780819446152", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "2002-12-24", "pages": "21-28" }, { "id": "authors:vc0vs-xxd31", "collection": "authors", "collection_id": "vc0vs-xxd31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-092915815", "type": "article", "title": "Carbon Abundances of Faint Stars in M13: Evidence of Two Abundance-altering Mechanisms", "author": [ { "family_name": "Briley", "given_name": "Michael M.", "clpid": "Briley-M-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Stetson", "given_name": "Peter B.", "orcid": "0000-0001-6074-6830", "clpid": "Stetson-P-B" } ], "abstract": "We present an analysis of CH band strengths in Keck Low-Resolution Imaging Spectrometer spectra of a sample of 81 stars in M13 within 2 mag of the main-sequence turnoff. The subgiants clearly exhibit a substantial (a factor of ~6) spread in [C/Fe]. Moreover, the bulk of the subgiants possess C abundances larger than those found among their more luminous counterparts. The turnoff stars themselves are too warm for appreciable CH formation, but the relatively small range in the observed CH band strength for stars just below the turnoff nevertheless translates into this same spread in [C/Fe]. Still fainter, the sample size is small, but the same range in [C/Fe] appears to be present. On the basis of these observations we suggest that a process external to the present stars has resulted in a substantial star-to-star dispersion in [C/Fe] (and possibly other light elements) among all stars in M13. In addition, the surface C abundances among the more luminous stars have been further modified by the operation of an internal deep-mixing mechanism during red giant branch ascent. The amplitude of the scatter we find in [C/Fe] at all luminosities may prove difficult to explain via accretion from intermediate-mass asymptotic giant branch stars as the external \"polluting\" mechanism.", "doi": "10.1086/345095", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2002-11-01", "series_number": "1", "volume": "579", "issue": "1", "pages": "L17-L20" }, { "id": "authors:jercs-b4t86", "collection": "authors", "collection_id": "jercs-b4t86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180207-101035264", "type": "article", "title": "Time delay and lens redshift for the doubly imaged BAL quasar SBS 1520+530", "author": [ { "family_name": "Burud", "given_name": "I.", "clpid": "Burud-I" }, { "family_name": "Hjorth", "given_name": "J.", "orcid": "0000-0002-4571-2306", "clpid": "Hjorth-J" }, { "family_name": "Courbin", "given_name": "F.", "clpid": "Courbin-F" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Magain", "given_name": "P.", "clpid": "Magain-P" }, { "family_name": "Jaunsen", "given_name": "A. O.", "clpid": "Jaunsen-A-O" }, { "family_name": "Kaas", "given_name": "A. A.", "clpid": "Kaas-A-A" }, { "family_name": "Faure", "given_name": "C.", "clpid": "Faure-C" }, { "family_name": "Letawe", "given_name": "G.", "clpid": "Letawe-G" } ], "abstract": "We present optical R-band light curves of the gravitationally lensed quasar SBS 1520+530 derived from data obtained at the Nordic Optical Telescope. A time delay of 130 \u00b1 3 days (1\u03c3) is determined from the light curves. In addition, spectra of SBS 1520+530 obtained at the Keck Observatory are spatially deconvolved in order to extract the spectrum of the faint lensing galaxy, free of any contamination by the light from the bright quasar images. This spectrum indicates a lens redshift z = 0.717, in agreement with one of the absorption systems found in the quasar spectra. The best mass model of the system includes a second nearby galaxy and a cluster of galaxies in addition to the main lensing galaxy. Adopting this model and an \u03a9 = 0.3, \u039b = 0.7 cosmology, our time-delay measurement yields a Hubble constant of H_0 = 51 \u00b1 9 km s^(-1) Mpc^(-1) (1\u03c3 error).", "doi": "10.1051/0004-6361:20020856", "issn": "0004-6361", "publisher": "EDP Sciences", "publication": "Astronomy & Astrophysics", "publication_date": "2002-08-02", "series_number": "2", "volume": "391", "issue": "2", "pages": "481-486" }, { "id": "authors:0m1pt-pmx60", "collection": "authors", "collection_id": "0m1pt-pmx60", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-132817785", "type": "article", "title": "Losing Weight: A Keck Spectroscopic Survey of the Massive Cluster of Galaxies RX J1347\u22121145", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Kneib", "given_name": "Jean-Paul", "orcid": "0000-0002-4616-4989", "clpid": "Kneib-J-P" } ], "abstract": "We present a sample of 47 spectroscopically confirmed members of RX J1347-1145, the most luminous X-ray cluster of galaxies discovered to date. With two exceptions, all the galaxies in this sample have red B-R colors and red spectral indices, with spectra similar to old local elliptical galaxies. Using all 47 cluster members, we derive a mean redshift of z = 0.4509 \u00b1 0.003 and a velocity dispersion of 910 \u00b1 130 km s^(-1), which corresponds to a virial mass of 4.4 \u00d7 10^(14) h^(-1) M\u2609 with a harmonic radius of 380 h^(-1) kpc. The derived total dynamical mass is marginally consistent with that deduced from the cluster's X-ray emission based on the analysis of ROSAT/ASCA images (Schindler and coworkers in 1997), but not consistent with the more recent X-ray analyses of Allen in 2000, Ettori, Allen, and Fabian in 2001, and Allen, Schmidt, and Fabian in 2002. Furthermore, the dynamical mass is significantly smaller than that derived from weak lensing (Fischer and Tyson in 1997) and from strong lensing (Sahu and coworkers in 1998). We propose that these various discrepant mass estimates may be understood if RX J1347-1145 is the product of two clusters caught in the act of merging in a direction perpendicular to the line of sight, although there is no evidence from the galaxy redshift distribution supporting this hypothesis. Even with this hypothesis, a significant part of the extremely high X-ray luminosity must still arise from nonvirialized, presumably shocked, gas. Finally, we report the serendipitous discovery of a lensed background galaxy at z = 4.083 that will put strong constraints on the lensing mass determination once its counterimage is securely identified.", "doi": "10.1086/340658", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2002-07-10", "series_number": "2", "volume": "573", "issue": "2", "pages": "524-532" }, { "id": "authors:h0rd5-ahd70", "collection": "authors", "collection_id": "h0rd5-ahd70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-113647897", "type": "article", "title": "Stellar Archaeology: A Keck Pilot Program on Extremely Metal-poor Stars from the Hamburg/ESO Survey. I. Stellar Parameters", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" }, { "family_name": "Beers", "given_name": "Timothy C.", "orcid": "0000-0003-4573-6233", "clpid": "Beers-T-C" }, { "family_name": "Gratton", "given_name": "Raffaele", "clpid": "Gratton-R" }, { "family_name": "Carretta", "given_name": "Eugenio", "clpid": "Carretta-E" } ], "abstract": "In this series of two papers, we present a high-dispersion spectroscopic analysis of eight candidate extremely metal-poor stars selected from the Hamburg/ESO Survey (HES) and of six additional very metal-poor stars. We demonstrate that with suitable vetting using moderate-resolution spectra, the yield of this survey for stars with [Fe/H] \u2264 -3.0 dex is very high; three out of the eight stars observed thus far at high resolution from the HES are actually that metal-poor, three more have [Fe/H] \u2264 -2.8 dex, and the remainder are only slightly more metal-rich. In preparation for a large-scale effort to mine the HES database for such stars about to get under way, we lay out in this paper the basic principles we intend to use to determine in a uniform way the stellar parameters T_(eff), log g, and reddening.", "doi": "10.1086/340954", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2002-07", "series_number": "1", "volume": "124", "issue": "1", "pages": "470-480" }, { "id": "authors:y3a15-f6425", "collection": "authors", "collection_id": "y3a15-f6425", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-113154333", "type": "article", "title": "Stellar Archaeology: A Keck Pilot Program on Extremely Metal-poor Stars from the Hamburg/ESO Survey. II. Abundance Analysis", "author": [ { "family_name": "Carretta", "given_name": "Eugenio", "clpid": "Carretta-E" }, { "family_name": "Gratton", "given_name": "Raffaele", "clpid": "Gratton-R" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Beers", "given_name": "Timothy C.", "orcid": "0000-0003-4573-6233", "clpid": "Beers-T-C" }, { "family_name": "Christlieb", "given_name": "Norbert", "orcid": "0000-0002-4043-2727", "clpid": "Christlieb-N" } ], "abstract": "We present a detailed abundance analysis of eight stars selected as extremely metal-poor candidates from the Hamburg/ESO Survey (HES). For comparison, we have also analyzed three extremely metal-poor candidates from the HK survey, and three additional bright metal-poor stars. With this work, we have doubled the number of extremely metal-poor stars ([Fe/H] \u2264 3.0 dex) with high-precision abundance analyses. Based on this analysis, our sample of extremely metal-poor candidates from the HES contains three stars with [Fe/H] \u2264 -3.0 dex, three more with [Fe/H] \u2264 -2.8 dex, and two stars that are only slightly more metal-rich. Thus, the chain of procedures that led to the selection of these stars from the HES successfully provides a high fraction of extremely metal-poor stars. We verify that our choices for stellar parameters, derived in Paper I and independently of the high-dispersion spectroscopic analysis, lead to acceptable ionization and excitation balances for Fe. Substantial non-LTE effects in Fe appear to be ruled out by the above agreement, even at these extremely low metallicities. For the \u03b1-elements Mg, Si, Ca, and Ti, the light element Al, the iron-peak elements Sc, Cr, and Mn, and the neutron-capture elements Sr and Ba, we find trends in abundance ratios [X/Fe] similar to those found by previous investigations. These trends appear to be identical for giants and for dwarfs. However, the scatter in most of these ratios, even at [Fe/H] \u2264 -3.0 dex, is surprisingly small. Only Sr and Ba, among the elements we examined, show scatter larger than the expected errors. Future work (the \"0Z Project\") will provide much stronger constraints on the scatter (or lack thereof) in elemental abundances for a substantially greater number of stars. We discuss the implications of these results for the early chemical evolution of the Galaxy, including such issues as the number of contributing supernovae and the sizes of typical protogalactic fragments in which they were born. In addition, we have identified a very metal-poor star in our sample that appears to represent the result of the s-process chain, operating in a very metal-poor environment, and exhibits extremely enhanced C, Ba, and Pb and somewhat enhanced Sr.", "doi": "10.1086/340955", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2002-07", "series_number": "1", "volume": "124", "issue": "1", "pages": "481-506" }, { "id": "authors:rea4x-bmd33", "collection": "authors", "collection_id": "rea4x-bmd33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-130213833", "type": "article", "title": "Abundances in Stars from the Red Giant Branch Tip to Near the Main-Sequence Turnoff in M71. III. Abundance Ratios", "author": [ { "family_name": "Ram\u00edrez", "given_name": "Solange V.", "clpid": "Ram\u00edrez-S-V" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present abundance ratios for 23 elements with respect to Fe in a sample of stars with a wide range in luminosity, from luminous giants to stars near the turnoff in a globular cluster. Our sample of 25 stars in M71 includes 10 giant stars more luminous than the red horizontal branch (RHB), three HB stars, nine giant stars less luminous than the RHB, and three stars near the turnoff. The analyzed spectra, obtained with HIRES at the Keck Observatory, are of high dispersion (R = \u03bb/\u0394\u03bb = 35,000). We find that the neutron capture, the iron peak, and the \u03b1-element abundance ratios show no trend with T_(eff) and low scatter around the mean between the top of the RGB and near the main-sequence turnoff. The \u03b1-elements Mg, Ca, Si, and Ti are overabundant relative to Fe. The anticorrelation between O and Na abundances observed in other metal-poor globular clusters is detected in our sample and extends to the main sequence. A statistically significant correlation between Al and Na abundances is observed among the M71 stars in our sample, extending to M_V = +1.8, fainter than the luminosity of the RGB bump in M5. Lithium is varying, as expected, and Zr may be varying from star to star as well. M71 appears to have abundance ratios very similar to M5, whose bright giants were studied by Ivans et al., but seems to have a smaller amplitude of star-to-star variations at a given luminosity, as might be expected from its higher metallicity. Neither extremely O-poor, Na-rich stars nor extremely O-rich, Na-poor, stars such as are observed in M5 and in M13, are present in our sample of M71 stars. The results of our abundance analysis of 25 stars in M71 provide sufficient evidence of abundance variations at unexpectedly low luminosities to rule out the mixing scenario. Either alone or, even more powerfully, combined with other recent studies of C and N abundances in M71 stars, the existence of such abundance variations cannot be reproduced within the context of our current understanding of stellar evolution.", "doi": "10.1086/340354", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2002-06", "series_number": "6", "volume": "123", "issue": "6", "pages": "3277-3297" }, { "id": "authors:p4zqn-knd81", "collection": "authors", "collection_id": "p4zqn-knd81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140703-135258516", "type": "publication_deliverable", "title": "California Extremely Large Telescope: Conceptual Design for a Thirty-Meter Telescope", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Dekany", "given_name": "Richard", "clpid": "Dekany-Richard" }, { "family_name": "Djorgovski", "given_name": "S. G.", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-S-G" }, { "family_name": "Ellis", "given_name": "Richard S.", "orcid": "0000-0001-7782-7071", "clpid": "Ellis-R-S" }, { "family_name": "Kulkarni", "given_name": "S. R.", "orcid": "0000-0001-5390-8563", "clpid": "Kulkarni-S-R" }, { "family_name": "MacMartin", "given_name": "Douglas G.", "orcid": "0000-0003-1987-9417", "clpid": "MacMartin-D-G" }, { "family_name": "Matthews", "given_name": "K.", "clpid": "Matthews-K" }, { "family_name": "Murray", "given_name": "Richard M.", "orcid": "0000-0002-5785-7481", "clpid": "Murray-R-M" }, { "family_name": "Padin", "given_name": "S.", "clpid": "Padin-S" }, { "family_name": "Sargent", "given_name": "Wallace L. W.", "clpid": "Sargent-W-L-W" }, { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" }, { "family_name": "Taylor", "given_name": "Keith", "clpid": "Taylor-K" }, { "family_name": "Tombrello", "given_name": "T. A.", "clpid": "Tombrello-T-A" }, { "literal": "California Institute of Technology" }, { "literal": "University of California" } ], "abstract": "Following great success in the creation of the Keck Observatory, scientists at the California Institute of\nTechnology and the University of California have begun to explore the scientific and technical prospects\nfor a much larger telescope. The Keck telescopes will remain the largest telescopes in the world for a\nnumber of years, with many decades of forefront research ahead after that. Though these telescopes\nhave produced dramatic discoveries, it is already clear that even larger telescopes must be built if we\nare to address some of the most profound questions about our universe. The time required to build a\nlarger telescope is approximately ten years, and the California community is presently well-positioned\nto begin its design and construction. The same scientists who conceived, led the design, and guided\nthe construction of the Keck Observatory have been intensely engaged in a study of the prospects for\nan extremely large telescope. Building on our experience with the Keck Observatory, we have concluded\nthat the large telescope is feasible and is within the bounds set by present-day technology. Our reference\ntelescope has a diameter of 30 meters, the largest size we believe can be built with acceptable risk. The\nproject is currently designated the California Extremely Large Telescope (CELT).", "publisher": "California Institute of Technology", "publication_date": "2002-06" }, { "id": "authors:ss6f4-mk253", "collection": "authors", "collection_id": "ss6f4-mk253", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-124543473", "type": "article", "title": "Carbon and Nitrogen Abundances in Stars at the Base of the Red Giant Branch in M5", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Briley", "given_name": "Michael M.", "clpid": "Briley-M-M" }, { "family_name": "Stetson", "given_name": "Peter B.", "orcid": "0000-0001-6074-6830", "clpid": "Stetson-P-B" } ], "abstract": "We present an analysis of a large sample of moderate resolution Keck LRIS spectra of subgiant (V ~ 17.2) and fainter stars in the Galactic globular cluster M5 (NGC 5904) with the goal of deriving C and N abundances. Star-to-star stochastic variations with significant range in both [C/Fe] and [N/Fe] are found at all luminosities extending to the bottom of the red giant branch at M_V ~ +3. Similar variations in CH appear to be present in the main-sequence turnoff spectra, but the signal in the current sample is too low for a detailed analysis. The variations seen among the M5 subgiants are consistent with the abundances found earlier by Briley et al. for brighter giants in this cluster. There is thus no sign of a change in the behavior of C and N with evolutionary stage over the full range in luminosity of the red giant and subgiant branches, although a systematic decrease with luminosity in the mean [C/H] smaller than a factor of 2 cannot be ruled out with confidence at present. The C and N abundances appear strongly anticorrelated, as would be expected from the CN-cycle processing of stellar material. Yet the present stars are considerably fainter than the red giant branch bump, the point at which deep mixing is believed to set in. On this basis, while the observed abundance pattern is consistent with proton capture nucleosynthesis, we infer that the site of the reactions is likely not within the present sample, but rather in a population of more massive (2\u20135 M\u2299), now-defunct stars. The range of variation of the N abundances is very large, and the sum of C+N increases as C decreases. To reproduce this requires the incorporation not only of CN but also of ON-processed material. Furthermore, the existence of this correlation is quite difficult to reproduce with an external mechanism such as \"pollution\" with material processed in a more massive asymptotic giant branch star, which mechanism is fundamentally stochastic in nature. We therefore suggest that although the internal mixing hypothesis has serious flaws, new theoretical insights are needed and it should not yet be ruled out.", "doi": "10.1086/340179", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2002-05", "series_number": "5", "volume": "123", "issue": "5", "pages": "2525-2540" }, { "id": "authors:by1g8-0tr20", "collection": "authors", "collection_id": "by1g8-0tr20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190522-134041052", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. XVI. The Luminosity Function for Galaxies in the Region of the Hubble Deep Field\u2013North to z\u2009 = \u20091.5", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We have carried out a study of the luminosity function (LF) of galaxies in the region of the Hubble Deep Field-North using our very complete redshift catalog. We divide the sample into five redshift bins covering the range 0.01 < z < 1.5 and consider three primary galaxy spectral classes. We solve for the LF at four rest-frame wavelengths from 0.24 to 2.2 \u03bcm. We find that the LFs for quiescent galaxies have shallow faint-end slopes while those of galaxies with detectable emission lines have steeper faint-end slopes. Furthermore, these slopes appear to be independent of redshift out to z = 1.05 for each galaxy spectral grouping and agree well with comparable local determinations. We then fix \u03b1 to obtain values of L* for each galaxy spectral grouping as a function of redshift. We find that galaxies with strong absorption lines become brighter with z with Q ~ 0.6 at all rest-frame bands studied here, where Q = \u0394 log [L*(z)]/\u0394z, while galaxies with detectable emission lines (i.e., star-forming galaxies) show a smaller change in L* with redshift at all bands, Q ~ 0.3, with Q becoming significantly larger at rest-frame 2400 \u00c5. Passive evolution models of galaxies are in reasonable agreement with these results for absorption-line-dominated galaxies, while plausible star formation histories can reproduce the behavior of the emission-line galaxies. We find a constant comoving number density and stellar mass in galaxies out to z ~ 1.05. By stretching all the correction factors applied to the galaxy counts in the highest redshift bin to their maximum possible values, we can just barely achieve this between z = 1.05 and 1.3. The major epoch(s) of star formation and of galaxy formation must have occurred even earlier. The UV luminosity density, an indicator of the star formation rate, has increased by a factor of ~4 over the period z = 0-1.", "doi": "10.1086/338226", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2002-03-10", "series_number": "2", "volume": "567", "issue": "2", "pages": "672-701" }, { "id": "authors:nx6vn-xcv45", "collection": "authors", "collection_id": "nx6vn-xcv45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-102115515", "type": "article", "title": "Abundances in Stars from the Red Giant Branch Tip to Near the Main-Sequence Turnoff in M71. II. Iron Abundance", "author": [ { "family_name": "Ram\u00edrez", "given_name": "Solange V.", "clpid": "Ram\u00edrez-S-V" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Buss", "given_name": "Jeremy", "clpid": "Buss-J" }, { "family_name": "Briley", "given_name": "Michael M.", "clpid": "Briley-M-M" } ], "abstract": "We present [Fe/H] abundance results that involve a sample of stars with a wide range in luminosity, from luminous giants to stars near the turnoff in a globular cluster. Our sample of 25 stars in M71 includes 10 giant stars more luminous than the RHB, three horizontal branch stars, nine giant stars less luminous than the RHB, and three stars near the turnoff. We analyzed both Fe I and Fe II lines in high-dispersion spectra observed with HIRES at the W. M. Keck Observatory. We find that the [Fe/H] abundances from both Fe I and Fe II lines agree with each other and with earlier determinations. Also the [Fe/H] obtained from Fe I and Fe II lines is constant within the rather small uncertainties for this group of stars over the full range in T_(eff) and luminosity, suggesting that non-LTE effects are negligible in our iron abundance determination. In this globular cluster, there is no difference among the mean [Fe/H] of giant stars located at or above the RHB, RHB stars, giant stars located below the RHB and stars near the turnoff.", "doi": "10.1086/322101", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2001-09", "series_number": "3", "volume": "122", "issue": "3", "pages": "1429-1437" }, { "id": "authors:c6evy-16865", "collection": "authors", "collection_id": "c6evy-16865", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-103624108", "type": "article", "title": "An Abundance Analysis for Four Red Horizontal-Branch Stars in the Extremely Metal-Rich Globular Cluster NGC 6528", "author": [ { "family_name": "Carretta", "given_name": "Eugenio", "clpid": "Carretta-E" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Gratton", "given_name": "Raffaele G.", "clpid": "Gratton-R-G" }, { "family_name": "Behr", "given_name": "Bradford B.", "clpid": "Behr-B-B" } ], "abstract": "We present the results of the first analysis of high-dispersion spectra of four red horizontal-branch stars in the metal-rich globular cluster NGC 6528, located in Baade's window. We find that the mean [Fe/H] for NGC 6528 is +0.07 \u00b1 0.01 dex (error of the mean), with a star-to-star scatter of \u03c3 = 0.02 dex (four stars), although the total error is likely to be larger (~0.1 dex) because of systematic errors related to the effective temperature scale and to model atmospheres. This metallicity is somewhat larger than both the mean abundance in the galactic bulge found by McWilliam & Rich (1994) and that found in our previous paper for NGC 6553. However, we find that the spectra of clump stars in NGC 6528 and 6553 are very similar each other, the slightly different metal abundances found being possibly due to the different atmospheric parameters adopted in the two analyses. Since the present analysis is based on higher quality material, we propose to revise our previous published metal abundance for NGC 6553 to [Fe/H] = -0.06 \u00b1 0.15. For NGC 6528, we find excesses for the \u03b1-process elements Si and Ca ([Si/Fe] = +0.4 and [Ca/Fe] = +0.2), whereas Mn is found to be underabundant ([Mn/Fe] = -0.4). We find a solar abundance of O; however, this is somewhat uncertain because of the dependence of the O abundance on the adopted atmospheric parameters and the coupling between C and O abundances in these cool, metal-rich stars. Finally, we find large Na excesses ([Na/Fe] ~ +0.4) in all stars examined.", "doi": "10.1086/322116", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2001-09", "series_number": "3", "volume": "122", "issue": "3", "pages": "1469-1485" }, { "id": "authors:7nqcj-5ce50", "collection": "authors", "collection_id": "7nqcj-5ce50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-100055784", "type": "article", "title": "Abundances in Stars from the Red Giant Branch Tip to Near the Main-Sequence Turnoff in M71. I. Sample Selection, Observing Strategy, and Stellar Parameters", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Behr", "given_name": "Bradford B.", "clpid": "Behr-B-B" }, { "family_name": "Briley", "given_name": "Michael M.", "clpid": "Briley-M-M" } ], "abstract": "We present the sample for an abundance analysis of 25 members of M71, with luminosities ranging from the red giant branch tip to the upper main sequence. The spectra are of high dispersion and of high precision. We describe the observing strategy and determine the stellar parameters for the sample stars using both broadband colors and fits of H\u03b1 profiles. The derived stellar parameters agree with those from the Yale^2 stellar evolutionary tracks to within 50\u2013100 K for a fixed log g, which is within the level of the uncertainties.", "doi": "10.1086/322100", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2001-09", "series_number": "3", "volume": "122", "issue": "3", "pages": "1420-1428" }, { "id": "authors:5sn6a-0hf64", "collection": "authors", "collection_id": "5sn6a-0hf64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170408-161252591", "type": "article", "title": "Discovery of a Galaxy Cluster via Weak Lensing", "author": [ { "family_name": "Wittman", "given_name": "D.", "orcid": "0000-0002-0813-5888", "clpid": "Wittman-D" }, { "family_name": "Tyson", "given_name": "J. A.", "clpid": "Tyson-J-A" }, { "family_name": "Margoniner", "given_name": "V. E.", "clpid": "Margoniner-V-E" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Dell'Antonio", "given_name": "I. P.", "clpid": "Dell'Antonio-I-P" } ], "abstract": "We report the discovery of a cluster of galaxies via its weak gravitational lensing effect on background galaxies, the first spectroscopically confirmed cluster to be discovered through its gravitational effects rather than by its electromagnetic radiation. This fundamentally different selection mechanism promises to yield mass-selected, rather than baryon- or photon-selected, samples of these important cosmological probes. We have confirmed this cluster with spectroscopic redshifts of 15 members at z = 0.276, with a velocity dispersion of 615 km s^(-1). We use the tangential shear as a function of source photometric redshift to estimate the lens redshift independently and find z_l = 0.30 \u00b1 0.08. The good agreement with the spectroscopy indicates that the redshift evolution of the mass function may be measurable from the imaging data alone in shear-selected surveys.", "doi": "10.1086/323173", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2001-08-20", "series_number": "2", "volume": "557", "issue": "2", "pages": "L89-L92" }, { "id": "authors:h4fhc-y8208", "collection": "authors", "collection_id": "h4fhc-y8208", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-093701611", "type": "article", "title": "Discovery of a Galaxy Cluster via Weak Lensing", "author": [ { "family_name": "Wittman", "given_name": "D.", "orcid": "0000-0002-0813-5888", "clpid": "Wittman-D" }, { "family_name": "Tyson", "given_name": "J. A.", "clpid": "Tyson-J-A" }, { "family_name": "Margoniner", "given_name": "V. E.", "clpid": "Margoniner-V-E" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Dell'Antonio", "given_name": "I. P.", "clpid": "Dell'Antonio-I-P" } ], "abstract": "We report the discovery of a cluster of galaxies via its weak gravitational lensing effect on background galaxies, the first spectroscopically confirmed cluster to be discovered through its gravitational effects rather than by its electromagnetic radiation. This fundamentally different selection mechanism promises to yield mass-selected, rather than baryon- or photon-selected, samples of these important cosmological probes. We have confirmed this cluster with spectroscopic redshifts of 15 members at z= 0.276, with a velocity dispersion of 615 km s^(-1). We use the tangential shear as a function of source photometric redshift to estimate the lens redshift independently and find z_l = 0.30 \u00b1 0.08. The good agreement with the spectroscopy indicates that the redshift evolution of the mass function may be measurable from the imaging data alone in shear-selected surveys.", "doi": "10.1086/323173", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2001-08-20", "series_number": "2", "volume": "557", "issue": "2", "pages": "L89-L92" }, { "id": "authors:gw7nt-bcv78", "collection": "authors", "collection_id": "gw7nt-bcv78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-090754573", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. XV. Classifications of Galaxies with 0.2 < z < 1.1 in the Hubble Deep Field North and its Flanking Fields", "author": [ { "family_name": "van den Bergh", "given_name": "Sidney", "clpid": "van-den-Bergh-S" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Crabbe", "given_name": "Christopher", "clpid": "Crabbe-C" } ], "abstract": "To circumvent the spatial effects of resolution on galaxy classification, the images of 233 objects of known redshift in the Hubble Deep Field (HDF) and its flanking fields that have redshifts in the range 0.20 < z < 1.10 were degraded to the resolution that they would have had if they were all located at a redshift of z = 1.00. As in Paper XIV of the present series, the effects of shifts in rest wavelength were mitigated by using R-band images for the classification of galaxies with 0.2 < z < 0.6 and I-band images for objects with redshifts 0.6 < z < 1.1. A special effort was made to search for bars in distant galaxies. The present data strongly confirm the previous conclusion that the Hubble tuning fork diagram only provides a satisfactory framework for the classification of galaxies with z < 0.3. More distant disk galaxies are often difficult to shoehorn into the Hubble classification scheme. The paucity of barred spirals and grand-design spirals at large redshifts is confirmed. It is concluded that the morphology of disk galaxies observed at look-back times smaller than 3\u20134 Gyr differs systematically from that of more distant galaxies viewed at look-back times of 4\u20138 Gyr. The disks of late-type spirals at z > 0.5 are seen to be more chaotic than those of their nearer counterparts. Furthermore, the spiral structure in distant early-type spirals appears to be less well developed than it is in nearby early galaxies.", "doi": "10.1086/321173", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2001-08", "series_number": "2", "volume": "122", "issue": "2", "pages": "611-620" }, { "id": "authors:9cm9f-hvk04", "collection": "authors", "collection_id": "9cm9f-hvk04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-091657621", "type": "article", "title": "Calibration of the CH and CN Variations Among Main-Sequence Stars in M71 and in M13", "author": [ { "family_name": "Briley", "given_name": "Michael M.", "clpid": "Briley-M-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "An analysis of the CN and CH band strengths measured in a large sample of M71 and M13 main-sequence stars by Cohen is undertaken using synthetic spectra to quantify the underlying C and N abundances. In the case of M71 it is found that the observed CN and CH band strengths are best matched by the identical C/N/O abundances which fit the bright giants, implying: (1) little if any mixing is taking place during red giant branch ascent in M71, and (2) a substantial component of the C and N abundance inhomogeneities is in place before the main-sequence turn-off. The unlikelihood of mixing while on the main sequence requires an explanation for the abundance variations which lies outside the present stars (primordial inhomogeneities or intracluster self enrichment). For M13 it is shown that the 3883 \u00c5 CN bands are too weak to be measured in the spectra for any reasonable set of expected compositions. A similar situation exists for CH as well. However, two of the more luminous program stars do appear to have C abundances considerably greater than those found among the bright giants, thereby suggesting deep mixing has taken place on the M13 red giant branch.", "doi": "10.1086/321115", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2001-07", "series_number": "1", "volume": "122", "issue": "1", "pages": "242-247" }, { "id": "authors:p1ae4-4ya04", "collection": "authors", "collection_id": "p1ae4-4ya04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-104207127", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. XIII. Spectral Energy Distributions for Galaxies in the Region of the Hubble Deep Field North", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We introduce a new empirical function for modeling the spectral energy distributions (SEDs) of galaxies. We apply it to a sample of 590 galaxies in the region of the Hubble Deep Field (HDF) with z< 1.5 using multicolor photometry with wide wavelength coverage combined with spectroscopic redshifts from our 93% complete R-selected redshift survey there. We find the following:\n1.\tAs expected, galaxies with strong signs of recent star formation (i.e., those that show emission lines) have bluer continua in both the rest-frame ultraviolet and optical/near-infrared.\n2.\tThe redder galaxies tend to be more luminous. Although galaxies with strong absorption lines and no emission features are ~15% of the total sample with 0.25 < z < 0.8, they are ~50% of the 25 most luminous galaxies in the sample at rest-frame R.\n3.\tThe SEDs of actively star-forming galaxies become bluer in the mean in the rest-frame UV at higher redshifts, a trend that might arise from SED modeling errors. Aside from this, we discern no change with redshift in the relationship between SED characteristics and galaxy spectral type based on the strength of narrow emission and absorption features.\n4.\tCombining with similar work at higher and lower redshift, the bluest galaxies have indistinguishable SEDs in the rest-frame UV over the redshift regime of 0\u20133.\nThere is no evidence in our R-selected sample that supports the existence of a substantial population of very dusty star-forming galaxies at z \u227e 1.5.\n5.\tOur ability to predict the mid-IR flux using the UV, optical, and near-IR SEDs is limited.\n6.\tThe potential accuracy of photometric redshifts is evaluated, bearing in mind that a break at 4000 \u00c5 must be detectable to within the errors of the photometry to assign a photo-z for galaxies in this redshift regime.\n7.\tThe rest-frame K-band luminosity as a function of redshift clearly shows a gradual change in the population of various types of galaxies, with star-forming galaxies becoming both more luminous and a larger fraction of the total population at higher redshifts.\n8.\tThe overall pattern of the L(K)-z relationship suggests that passive evolution at constant stellar mass is a good approximation to the actual behavior of at least the most luminous galaxies in this large sample of galaxies in the region of the HDF out to z ~ 1.5.", "doi": "10.1086/321066", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2001-06", "series_number": "6", "volume": "121", "issue": "6", "pages": "2895-2914" }, { "id": "authors:8x7hk-pvx61", "collection": "authors", "collection_id": "8x7hk-pvx61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-105813534", "type": "article", "title": "Lost and Found: The Damped Ly\u03b1 Absorbers in the QSO OI 363", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "The galaxy giving rise to the damped Ly\u03b1 absorbing system with z = 0.221 in the QSO OI 363 has been found. A galaxy that is probably associated with the second damped Ly\u03b1 absorber (DLA) in the same QSO (z = 0.0912) has also been found. Neither galaxy is very luminous, and neither galaxy shows signs of extensive current star formation, a massive disk, or lots of gas. The impact parameters for both galaxies with respect to the QSO are reasonable. If most DLAs arise in such low-luminosity galaxies, it will be difficult to pick out the correct source galaxy for DLA systems at high redshift, given the large projected areal density on the sky of faint galaxies around distant QSOs.", "doi": "10.1086/319396", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2001-03", "series_number": "3", "volume": "121", "issue": "3", "pages": "1275-1277" }, { "id": "authors:ds38m-9xq30", "collection": "authors", "collection_id": "ds38m-9xq30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-131920716", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. XII. Clustering of Galaxies", "author": [ { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" } ], "abstract": "A clustering analysis is performed on two samples of ~600 faint galaxies each, in two widely separated regions of the sky, including the Hubble Deep Field. One of the survey regions is configured so that some galaxy pairs span angular separations of up to 1\u00b0. The median redshift is z_(med) \u2248 0.55. Strong clustering is obvious, with every pencil-beam field containing a handful of narrow redshift-space features, corresponding to galaxy structures with sizes of 5-20 Mpc. The structures are not obviously organized on planes, although one prominent, colinear triplet of structures is observed, spanning ~20 Mpc. This may be evidence of a filament. A galaxy-galaxy correlation function calculation is performed. No significant evolution of clustering (relative to stable clustering) is found in the redshift range 0.3 < z < 1.0. This is not surprising, since uncertainties in the correlation amplitude estimated from surveys such as these are large; field-to-field variations and covariances between data points are both shown to be significant. Consistent with other studies in this redshift range, the galaxy-galaxy correlation length is found to be somewhat smaller than that predicted from local measurements and an assumption of no evolution. Galaxies with absorption-line-dominated spectra show much stronger clustering at distances of <2 Mpc than typical field galaxies. There is some evidence for weaker clustering at intermediate redshift than at low redshift, when the results presented here are compared with surveys of the local universe. In subsets of the data, the measured pairwise velocity dispersion of galaxies ranges from 200 to 600 km s^(-1), depending on the properties of the dominant redshift structures in each subset.", "doi": "10.1086/317779", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2000-12-10", "series_number": "1", "volume": "545", "issue": "1", "pages": "32-42" }, { "id": "authors:h2pk5-32r62", "collection": "authors", "collection_id": "h2pk5-32r62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-132511021", "type": "article", "title": "RX J0911+05: A Massive Cluster Lens at z =\u2009 0.769", "author": [ { "family_name": "Kneib", "given_name": "Jean-Paul", "orcid": "0000-0002-4616-4989", "clpid": "Kneib-J-P" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Hjorth", "given_name": "Jens", "orcid": "0000-0002-4571-2306", "clpid": "Hjorth-J" } ], "abstract": "We report the detection of a massive high-redshift cluster of galaxies near the quadruple quasar RX J0911+05, using the Low-Resolution Imaging Spectrograph instrument on the Keck II telescope. The cluster is found to have a mean redshift of z = 0.7689 \u00b1 0.002 and a velocity dispersion of \u03c3 = 836^(+180)_(-200) km s^(-1), based on redshift measurements for 24 member galaxies. This massive high-redshift cluster is the origin of the unusually large external shear required by lensing models of the quadruple quasar system. We predict the expected time delay depending on the exact contribution of the cluster. A measurement of the time delay and further deep lensing and X-ray observations will unravel useful properties of this serendipitously discovered high-redshift cluster and may put interesting cosmological constraints on H_0.", "doi": "10.1086/317285", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2000-11-20", "series_number": "1", "volume": "544", "issue": "1", "pages": "L35-L39" }, { "id": "authors:r2r1p-nrn20", "collection": "authors", "collection_id": "r2r1p-nrn20", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-124703418", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. XIV. Galaxy Morphology in the Hubble Deep Field (North) and Its Flanking Fields to z =\u2009 1.2", "author": [ { "family_name": "van den Bergh", "given_name": "Sidney", "clpid": "van-den-Bergh-S" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" } ], "abstract": "Morphological classifications are reported for Hubble Space Telescope images of 241 galaxies in the Hubble Deep Field and its flanking fields with measured redshifts in the interval 0.25 < z < 1.2, drawn from a magnitude-limited redshift survey to R = 24.0. The galaxies are divided into three groups with redshifts in the intervals 0.25\u20130.6, 0.6\u20130.8, and 0.8\u20131.2. R_(606) images from the first group and I_(814) images from the second and third groups are compared with B-band images of nearby galaxies. All classifications were therefore made at approximately the same rest wavelength. Selection biases are discussed. We corroborate and extend the results of earlier investigations by observing that\n1.\tMost intermediate- and late-type galaxies with z \u2273 0.5 have morphologies that are dramatically different from those of local galaxies and cannot be shoehorned into the Hubble \"tuning fork\" classification scheme;\n2.\tGrand-design spirals appear to be rare or absent for z \u2273 0.3;\n3.\tMany Sa and Sb spirals with z \u2273 0.6 do not exhibit well-defined spiral arms, and the arms of distant Sc galaxies appear more chaotic than those of their nearby counterparts;\n4.\tThe fraction of all galaxies that are of types Sc and Scd drops from 23% at z ~ 0 to 5% for z > 0.6.\n5.\tBarred spirals are extremely rare for z \u2273 0.5;\n6.\tRoughly one in five galaxies with z \u2273 0.8 is a compact objects that resembles local E, S0, or Sa galaxies.\n7.\tPeculiar galaxies are more common beyond z = 0.3, especially among late-type spirals, than they are at z ~ 0;\n8.\tMerging galaxies, particularly those with three or more components, also become more common with increasing redshift.\nOn the basis of these and similar observations, it is inferred that the development of pronounced spiral structure was delayed until ~5 Gyr and that most bulges are probably not formed by disintegrating bars. Major morphological changes were still taking place only ~5 Gyr ago, even though changes in the integrated light of most galaxies were then much slower than they were ~10 Gyr ago.", "doi": "10.1086/316828", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2000-11", "series_number": "5", "volume": "120", "issue": "5", "pages": "2190-2205" }, { "id": "authors:cntpw-ff085", "collection": "authors", "collection_id": "cntpw-ff085", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103833418", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. X. A Redshift Survey in the Region of the Hubble Deep Field North", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Cowie", "given_name": "Lennox L.", "orcid": "0000-0002-6319-1575", "clpid": "Cowie-L-L" }, { "family_name": "Hu", "given_name": "Esther", "clpid": "Hu-Esther-M" }, { "family_name": "Songaila", "given_name": "Antoinette", "clpid": "Songaila-A" }, { "family_name": "Shopbell", "given_name": "Patrick", "clpid": "Shopbell-P-L" }, { "family_name": "Richberg", "given_name": "Kevin", "clpid": "Richberg-K" } ], "abstract": "A redshift survey has been carried out in the region of the Hubble Deep Field North using the Low Resolution Imaging Spectrograph (LRIS) at the Keck Observatory. The resulting redshift catalog, which contains 671 entries, is a compendium of our own data together with published LRIS/Keck data. It is more than 92% complete for objects, irrespective of morphology, to R = 24 mag in the HDF itself and to R = 23 mag in the flanking fields within a diameter of 8' centered on the HDF, an unusually high completion for a magnitude-limited survey performed with a large telescope. A median redshift z = 1.0 is reached at R ~ 23.8. Strong peaks in the redshift distribution, which arise when a group or poor cluster of galaxies intersect the area surveyed, can be identified to z ~ 1.2 in this data set. More than 68% of the galaxies are members of these redshift peaks. In a few cases, closely spaced peaks in z can be resolved into separate groups of galaxies that can be distinguished in both velocity and location on the sky. The radial separation of these peaks in the pencil-beam survey is consistent with a characteristic length scale for the their separation of \u224870 Mpc in our adopted cosmology (h = 0.6, \u03a9_M = 0.3, \u039b = 0). Strong galaxy clustering is in evidence at all epochs back to z \u2264 1.1. A near-infrared selected sample with K < 20 was also constructed in this field. Extremely red objects with R-K > 5.0 comprise 7% of the total K-selected sample. This fraction rises rapidly toward fainter K magnitude, reaching about 10% at K ~ 19.7. We have attempted to identify the radio sources in the region of the HDF. The secure radio sources seem to divide into two classes. The first have reasonably bright galaxies at moderate redshifts as optical counterparts, while the second, comprising about 1/3 of the total, have extremely faint optical counterparts (R \u2265 25 mag). These do not represent a continuous extrapolation in any property (z or dust content) of the first group. We identify ~2/3 of the secure mid-IR sources in the region of the HDF with normal galaxies with z < 1.3. The ratio of the mid-IR to optical flux increases as z increases, but this is due primarily to selection effects, and the same trend is seen in the radio sources. We suggest that the mid-IR emission is more tightly coupled to the rate of ongoing star formation than is the radio emission. We also demonstrate that the best photometric redshift techniques are capable of reaching a precision of \u03c3[(z_(phot) - z_(spec))/(1 + z_(spec))] = 0.05 for the majority of galaxies with z < 1.3. The two broad-lined AGNs with z < 3 are the brightest objects in the redshift peak at z ~ 0.96.", "doi": "10.1086/309096", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2000-07-20", "series_number": "1", "volume": "538", "issue": "1", "pages": "29-52" }, { "id": "authors:xvc9g-ynj83", "collection": "authors", "collection_id": "xvc9g-ynj83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170223-133457249", "type": "article", "title": "3 Micron Imaging of the Hubble Deep Field", "author": [ { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Neugebauer", "given_name": "Gerry", "clpid": "Neugebauer-G" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Dickinson", "given_name": "Mark", "orcid": "0000-0001-5414-5131", "clpid": "Dickinson-Mark-E" }, { "family_name": "Djorgovski", "given_name": "S. G.", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-S-G" }, { "family_name": "Matthews", "given_name": "Keith", "clpid": "Matthews-Keith-Astronomy" }, { "family_name": "Soifer", "given_name": "B. T.", "orcid": "0000-0002-8112-1132", "clpid": "Soifer-B-T" } ], "abstract": "Images of the Hubble Deep Field (HDF) at 3.2 \u03bcm, taken with the 10 m Keck Telescope, are presented. The images cover a total area of ~2.5 arcmin^2. To a 5 \u03c3 limit of [3.2]_(tot) \u2248 17.5 mag (Vega relative), 11 sources are detected, nine of which are extragalactic. The integrated galaxy number counts are therefore ~1.3 \u00d7 10^4 deg^(-2) to this depth. The galaxies detected at 3.2 \u03bcm have a median redshift of z = 0.56. All 3.2 \u03bcm sources have 1.6 \u03bcm, 1.1 \u03bcm, and visual counterparts, all of fairly regular morphology; several also have 6.7 \u03bcm, 15 \u03bcm, 850 \u03bcm, 8.5 GHz, or 1.4 GHz counterparts. No sources are found that are either anomalously red or anomalously blue in their H-[3.2] color, and there are significant detections of most of the known near-infrared HDF sources for which detection in these 3.2 \u03bcm data seemed likely.", "doi": "10.1086/301309", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2000-04", "series_number": "4", "volume": "119", "issue": "4", "pages": "1519-1525" }, { "id": "authors:0dmtb-t2x95", "collection": "authors", "collection_id": "0dmtb-t2x95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-135650384", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. XI. The Merger Rate to Redshift 1 from Kinematic Pairs", "author": [ { "family_name": "Carlberg", "given_name": "R. G.", "clpid": "Carlberg-R-G" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Patton", "given_name": "D. R.", "clpid": "Patton-D-R" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Yee", "given_name": "H. K. C.", "clpid": "Yee-H-K-C" }, { "family_name": "Morris", "given_name": "S. L.", "clpid": "Morris-S-L" }, { "family_name": "Lin", "given_name": "H.", "clpid": "Lin-H" }, { "family_name": "Hall", "given_name": "Patrick B.", "clpid": "Hall-P-B" }, { "family_name": "Sawicki", "given_name": "M.", "orcid": "0000-0002-7712-7857", "clpid": "Sawicki-M" }, { "family_name": "Wirth", "given_name": "Gregory D.", "clpid": "Wirth-G-D" }, { "family_name": "Cowie", "given_name": "Lennox L.", "orcid": "0000-0002-6319-1575", "clpid": "Cowie-L-L" }, { "family_name": "Hu", "given_name": "Esther", "clpid": "Hu-Esther-M" }, { "family_name": "Songaila", "given_name": "Antoinette", "clpid": "Songaila-A" } ], "abstract": "The rate of mass accumulation due to galaxy merging depends on the mass, density, and velocity distribution of galaxies in the near neighborhood of a host galaxy. The fractional luminosity in kinematic pairs combines all of these effects in a single estimator that is relatively insensitive to population evolution. Here we use a k-corrected and evolution-compensated volume-limited sample having an R-band absolute magnitude of M^(k,e)_R \u2264 -19.8 + 5 log h mag drawing about 300 redshifts from the Caltech Faint Galaxy Redshift Survey and 3000 from the Canadian Network for Observational Cosmology field galaxy survey to measure the rate and redshift evolution of merging. The combined sample has an approximately constant comoving number and luminosity density from redshift 0.1 to 1.1 (\u03a9_M = 0.2, \u03a9_\u039b = 0.8); hence, any merger evolution will be dominated by correlation and velocity evolution, not density evolution. We identify kinematic pairs with projected separations less than either 50 or 100 h^(-1) kpc and rest-frame velocity differences of less than 1000 km s^(-1). The fractional luminosity in pairs is modeled as f_L(\u0394v, r_p, M^(k,e)_\u03c4)(1 + z)^(m,L), where [f_L, m_L] are [0.14 \u00b1 0.07, 0 \u00b1 1.4] and [0.37 \u00b1 0.7, 0.1 \u00b1 0.5] for r_p \u2264 50 and 100 h^(-1) kpc, respectively (\u03a9_M = 0.2, \u03a9_\u039b = 0.8). The value of mL is about 0.6 larger if \u039b = 0. To convert these redshift-space statistics to a merger rate, we use the data to derive a conversion factor to a physical space pair density, a merger probability, and a mean in-spiral time. The resulting mass accretion rate per galaxy (M_1, M_2 \u2265 0.2M*) is 0.02 \u00b1 0.01(1 + z)^(0.1\u00b10.5)M* Gyr^(-1). Present-day high-luminosity galaxies therefore have accreted approximately 0.15M* of their mass over the approximately 7 Gyr to redshift 1. Since merging is likely only weakly dependent on the host mass, the fractional effect, \u03b4M/M 0.15M*/M, is dramatic for lower mass galaxies but is, on the average, effectively perturbative for galaxies above 1M*.", "doi": "10.1086/312560", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2000-03-20", "series_number": "1", "volume": "532", "issue": "1", "pages": "L1-L4" }, { "id": "authors:gdjw9-4f348", "collection": "authors", "collection_id": "gdjw9-4f348", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-135043421", "type": "article", "title": "Rotations and Abundances of Blue Horizontal-Branch Stars in Globular Cluster M15", "author": [ { "family_name": "Behr", "given_name": "Bradford B.", "clpid": "Behr-B-B" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "McCarthy", "given_name": "James K.", "clpid": "McCarthy-J-K" } ], "abstract": "High-resolution optical spectra of 18 blue horizontal-branch stars in the globular cluster M15 indicate that their stellar rotation rates and photospheric compositions vary strongly as a function of effective temperature. Among the cooler stars in the sample, at T_(eff) ~ 8500 K, metal abundances are in rough agreement with the canonical cluster metallicity, and the v sin i rotations appear to have a bimodal distribution, with eight stars at v sin i < 15 km s^(-1) and two stars at v sin i ~ 35 km s^(-1). Most of the stars at T_(eff) \u2265 10,000 K, however, are slowly rotating, v sin i < 7 km s^(-1), and their iron and titanium are enhanced by a factor of 300 to solar abundance levels. Magnesium maintains a nearly constant abundance over the entire range of T_(eff), and helium is depleted by factors of 10-30 in three of the hotter stars. Diffusion effects in the stellar atmospheres are the most likely explanation for these large differences in composition. Our results are qualitatively very similar to those previously reported for M13 and NGC 6752, but with even larger enhancement amplitudes, presumably due to the increased efficiency of radiative levitation at lower intrinsic [Fe/H]. We also see evidence for faster stellar rotation explicitly preventing the onset of the diffusion mechanisms among a subset of the hotter stars.", "doi": "10.1086/312524", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2000-03-01", "series_number": "1", "volume": "531", "issue": "1", "pages": "L37-L40" }, { "id": "authors:qp14j-9qs15", "collection": "authors", "collection_id": "qp14j-9qs15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170228-080833641", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. IX. Source Detection and Photometry in the Hubble Deep Field Region", "author": [ { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Pahre", "given_name": "Michael A.", "clpid": "Pahre-M-A" }, { "family_name": "Adelberger", "given_name": "Kurt L.", "clpid": "Adelberger-K-L" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Gautier", "given_name": "T. N.", "clpid": "Gautier-T-N-III" }, { "family_name": "Jarrett", "given_name": "Thomas", "orcid": "0000-0002-4939-734X", "clpid": "Jarrett-T-H" }, { "family_name": "Neugebauer", "given_name": "Gerry", "clpid": "Neugebauer-G" }, { "family_name": "Steidel", "given_name": "Charles C.", "orcid": "0000-0002-4834-7260", "clpid": "Steidel-C-C" } ], "abstract": "Detection and photometry of sources in the U_n, G, \u211b, and K_s bands in a 9 \u00d7 9 arcmin^2 region of the sky, centered on the Hubble Deep Field, are described. The data permit construction of complete photometric catalogs to roughly U_n = 25, G = 26, \u211b = 25.5, K_s = 20 mag and significant photometric measurements somewhat fainter. The galaxy number density is 1.3 \u00d7 10^5 deg^(-2) to \u211b = 25.0 mag. Galaxy number counts have slopes d log N/dm = 0.42, 0.33, 0.27, and 0.31 in the U_n, G, \u211b, and K_s bands, consistent with previous studies and the trend that fainter galaxies are, on average, bluer. Galaxy catalogs selected in the \u211b and K_s bands are presented, containing 3607 and 488 sources in field areas of 74.8 and 59.4 arcmin^2, to \u211b = 25.5 and K_s = 20 mag.", "doi": "10.1086/313318", "issn": "0067-0049", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Supplement Series", "publication_date": "2000-03", "series_number": "1", "volume": "127", "issue": "1", "pages": "1-9" }, { "id": "authors:y8dqv-4ys46", "collection": "authors", "collection_id": "y8dqv-4ys46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-141458208", "type": "article", "title": "A New Spin on the Problem of Horizontal\u2010Branch Gaps: Stellar Rotation along the Blue Horizontal Branch of Globular Cluster M13", "author": [ { "family_name": "Behr", "given_name": "Bradford B.", "clpid": "Behr-B-B" }, { "family_name": "Djorgovski", "given_name": "S. G.", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-S-G" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "McCarthy", "given_name": "James K.", "clpid": "McCarthy-J-K" }, { "family_name": "C\u00f4t\u00e9", "given_name": "Patrick", "orcid": "0000-0003-1184-8114", "clpid": "C\u00f4t\u00e9-P" }, { "family_name": "Piotto", "given_name": "Giampaolo", "clpid": "Piotto-G" }, { "family_name": "Zoccali", "given_name": "Manuela", "clpid": "Zoccali-M" } ], "abstract": "We have determined the projected rotational velocities of 13 blue horizontal-branch (BHB) stars in the globular cluster M13 via rotational broadening of metal absorption lines. Our sample spans the photometric gap observed in the horizontal-branch distribution at T_(eff) 11,000 K and reveals a pronounced difference in stellar rotation on either side of this feature\u2014blueward of the gap, all the stars show modest rotations, v sin i < 10 km s^(-1), while to the red side of the gap, we confirm the more rapidly rotating population (v sin i \u2243 40 km s^(-1)) previously observed by R. C. Peterson and coworkers. Taken together with these prior results, our measurements indicate that a star's rotation is indeed related to its location along the HB, although the mechanism behind this correlation remains unknown. We explore possible connections between stellar rotation and mass-loss mechanisms which influence the photometric morphology of globular cluster HBs.", "doi": "10.1086/308219", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "2000-01-10", "series_number": "2", "volume": "528", "issue": "2", "pages": "849-853" }, { "id": "authors:53smy-vy524", "collection": "authors", "collection_id": "53smy-vy524", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-140827369", "type": "article", "title": "The Kinematics of the Outer Halo of M87", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Radial velocities are presented for a new sample of globular clusters in the outer halo of M87 at a distance of 300''\u2013540'' (24\u201343 kpc) from the center of this galaxy. These are used to augment our previously published data, and an analysis of the rotation and velocity dispersion of the M87 globular cluster system is carried out. The rotation is ~300 km s^(-1) at R = 32 kpc, at which point the velocity dispersion is also still quite high, ~450 km s^(-1). The high rotation is interesting. The outer halo of M87 is, as was found in our previous kinematic analysis, very massive.", "doi": "10.1086/301184", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "2000-01", "series_number": "1", "volume": "119", "issue": "1", "pages": "162-165" }, { "id": "authors:mpp9b-z1x50", "collection": "authors", "collection_id": "mpp9b-z1x50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-104736397", "type": "book_section", "title": "Clustering in the Caltech Faint Galaxy Redshift Survey", "book_title": "Clustering at High Redshift", "author": [ { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Mazure", "given_name": "A.", "clpid": "Mazure-A" }, { "family_name": "Le F\u00e8vre", "given_name": "O.", "clpid": "Le-F\u00e8vre-O" }, { "family_name": "Le Brun", "given_name": "V.", "clpid": "Le-Brun-V" } ], "abstract": "The Caltech Faint Galaxy Redshift Survey has collected \u223c2000 spectra taken with multi-slit masks using the Low Resolution Imaging Spectrograph at the Keck Observatory (Oke et al 1995) in two widely separated fields on the sky, each \u223c1 x 1 deg^2. Most of these objects are faint field galaxies; about 10% are Galactic stars and about 1% are broad-lined AGNs. \nI summarize the small scale clustering of this sample as well as the evidence in support of large scale structure.", "doi": "10.48550/arXiv.9910242", "isbn": "9781583810279", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "2000", "pages": "314-318" }, { "id": "authors:bn6ke-bbe26", "collection": "authors", "collection_id": "bn6ke-bbe26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190611-074244010", "type": "book_section", "title": "Variations in abundances among main sequence stars in M71", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Briley", "given_name": "Michael M.", "clpid": "Briley-M-M" } ], "contributor": [ { "family_name": "Noels", "given_name": "A.", "clpid": "Noels-A" }, { "family_name": "Magain", "given_name": "P.", "clpid": "Magain-P" }, { "family_name": "Caro", "given_name": "D.", "clpid": "Caro-D" }, { "family_name": "Jehin", "given_name": "E.", "clpid": "Jehin-E" }, { "family_name": "Parmentier", "given_name": "G.", "clpid": "Parmentier-G" }, { "family_name": "Thoul", "given_name": "A.", "clpid": "Thoul-A" } ], "abstract": "CH and CN variations are definitely present among the main sequence stars in a narrow range of luminosity just below the turnoff in the globular cluster stars. We show that the same set of C, N and O abundances that are used to fit the CN band in the CN-strong and CN-weak giants and subgiants in this cluster also successfully reproduce the behavior of the CH and CN molecular bands seen in the main sequence sample. This strongly suggests that the variations seen in M71 are primordial in origin. A hint of variation in the strength of the NaD lines is also seen in the main\nsequence sample. A range in Na abundance of about a factor of 3 is required to explain this. Strong Na among the main sequence stars appears to be correlated with strong CN, which is also characteristic\nof Na variations among red giants in globular clusters.", "publisher": "Universite de Li\u00e8ge", "publication_date": "2000" }, { "id": "authors:68pqk-1hp37", "collection": "authors", "collection_id": "68pqk-1hp37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170215-100325608", "type": "article", "title": "Near-Infrared Observations of the Extremely Red Object Cl 0939+4713B: An Old Galaxy at z ~ 1.58?", "author": [ { "family_name": "Soifer", "given_name": "B. T.", "orcid": "0000-0002-8112-1132", "clpid": "Soifer-B-T" }, { "family_name": "Matthews", "given_name": "K.", "clpid": "Matthews-Keith-Astronomy" }, { "family_name": "Neugebauer", "given_name": "G.", "clpid": "Neugebauer-G" }, { "family_name": "Armus", "given_name": "L.", "orcid": "0000-0003-3498-2973", "clpid": "Armus-L" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Smail", "given_name": "I.", "orcid": "0000-0003-3037-257X", "clpid": "Smail-I" } ], "abstract": "Near-infrared imaging and spectroscopic observations of the extremely red object Cl 0939+4713B (R-K ~ 7 mag) have been obtained with the Near Infrared Camera on the Keck I Telescope of the W. M. Keck Observatory. The imaging shows a slightly elongated structure, while the spectroscopy shows a continuum break that allows us to determine a redshift of z = 1.58^(+0.01)_(-0.03) for this system. The fits of a range of models to the infrared spectrum suggest that it is predominantly an old (>10^9 yr) stellar system that suffers little extinction, while the measured R and I magnitudes suggest an age of ~3 \u00d7 10^8 yr. The limit on the equivalent width of any emission line in the infrared spectrum suggests that Cl 0939+4713B is not an actively star-forming galaxy. This system, though similar in R-K color to the object HR 10 (also known as J1645+46), is much different in morphology and emission-line strengths, demonstrating the heterogeneity of extremely red extragalactic objects selected on the basis of large R-K values.", "doi": "10.1086/301071", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1999-11", "series_number": "5", "volume": "118", "issue": "5", "pages": "2065-2070" }, { "id": "authors:4a4st-fc128", "collection": "authors", "collection_id": "4a4st-fc128", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190528-134609249", "type": "article", "title": "An Abundance Analysis for Five Red Horizontal-Branch Stars in the Extremely Metal-rich Globular Cluster NGC 6553", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Gratton", "given_name": "Raffaele G.", "clpid": "Gratton-R-G" }, { "family_name": "Behr", "given_name": "Bradford B.", "clpid": "Behr-B-B" }, { "family_name": "Carretta", "given_name": "Eugenio", "clpid": "Carretta-E" } ], "abstract": "We provide a high-dispersion line-by-line abundance analysis of five red horizontal-branch (HB) stars in the extremely metal-rich Galactic globular cluster NGC 6553. These red HB stars are significantly hotter than the very cool stars near the tip of the giant branch in such a metal-rich globular cluster, and hence their spectra are much more amenable to an abundance analysis than would be the case for red giants. We find that the mean [Fe/H] for NGC 6553 is -0.16 dex, comparable to the mean abundance in the Galactic bulge found by McWilliam & Rich and considerably higher than that obtained from an analysis of two red giants in this cluster by Barbuy and coworkers. The relative abundance for the best-determined \u03b1-process element (Ca) indicates an excess of \u03b1-process elements of about a factor of 2. The metallicity of NGC 6553 reaches the average of the Galactic bulge and of the solar neighborhood.", "doi": "10.1086/307765", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1999-10-01", "series_number": "2", "volume": "523", "issue": "2", "pages": "739-751" }, { "id": "authors:6tcwp-a0641", "collection": "authors", "collection_id": "6tcwp-a0641", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-144115768", "type": "article", "title": "Abundances of Red Giants in the Andromeda II Dwarf Spheroidal Galaxy", "author": [ { "family_name": "C\u00f4t\u00e9", "given_name": "Patrick", "orcid": "0000-0003-1184-8114", "clpid": "C\u00f4t\u00e9-P" }, { "family_name": "Oke", "given_name": "J. B.", "clpid": "Oke-J-B" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We have obtained spectra for 50 candidate red giants in Andromeda II, a dwarf spheroidal companion of M31, using the Low Resolution Imaging Spectrometer on the Keck II Telescope. After eliminating background galaxies and Galactic foreground stars, we are left with a sample of 42 red giants for which membership in Andromeda II can be established unambiguously from radial velocities. Line indexes measured on the Lick/IDS system are combined with VI photometry obtained with the Keck II and Palomar 5 m telescopes to investigate the age and metallicity distribution of these stars. Based on a comparison of the measured line indexes with those of Lick/IDS standard stars in globular and open clusters, we derive a mean metallicity of \u3008[Fe/H]\u3009 = -1.47 \u00b1 0.19 dex. This confirms the earlier conclusion, based on Thuan-Gunn gr photometry, that Andromeda II obeys the familiar relation between mean stellar metallicity and galaxy luminosity. There is also evidence for a dispersion in metallicity of \u03c3([Fe/H]) = 0.35 \u00b1 0.10 dex, based on the scatter in the measured Mg b line indexes and the observed width of the galaxy's giant branch. We note that, while existing observations of Local Group dwarf galaxies indicate that their mean metallicity depends rather sensitively on total luminosity, the internal spread in metallicity appears to be relatively independent of galaxy luminosity.\nOur spectroscopic sample contains one carbon star. We measure MI \u2243-3.8 for this star, which places it below the tip of the red giant branch and suggests a common origin with the CH stars found in the Galactic halo. Although this carbon star alone does not provide evidence of an intermediate-age component in Andromeda II, two other stars in our spectroscopic sample have MI \u2243-4.7 and -4.5. Membership in Andromeda II is unambiguous in both cases, indicating that these stars fall along an extended asymptotic giant branch and pointing to the presence of a modest intermediate-age population in this galaxy.", "doi": "10.1086/301054", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1999-10", "series_number": "4", "volume": "118", "issue": "4", "pages": "1645-1656" }, { "id": "authors:3a6s7-ajm31", "collection": "authors", "collection_id": "3a6s7-ajm31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190528-140622271", "type": "article", "title": "Striking Photospheric Abundance Anomalies in Blue Horizontal-Branch Stars in Globular Cluster M13", "author": [ { "family_name": "Behr", "given_name": "Bradford B.", "clpid": "Behr-B-B" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "McCarthy", "given_name": "James K.", "clpid": "McCarthy-J-K" }, { "family_name": "Djorgovski", "given_name": "S. George", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-S-G" } ], "abstract": "High-resolution optical spectra of 13 blue horizontal-branch stars in the globular cluster M13 show enormous deviations in element abundances from the expected cluster metallicity. In the hotter stars (T_(eff) > 12,000 K), helium is depleted by factors of 10-100 below solar, while iron is enhanced to 3 times the solar abundance, 2 orders of magnitude above the canonical metallicity of [Fe/H] \u2243-1.5 dex for this globular cluster. Nitrogen, phosphorus, and chromium exhibit even more pronounced enhancements, and other metals are also mildly overabundant, with the exception of magnesium, which stays very near the expected cluster metallicity. These photospheric anomalies are most likely due to diffusion\u2014the gravitational settling of helium and the radiative levitation of the other elements\u2014in the stable radiative atmospheres of these hot stars. The effects of these mechanisms may have some impact on the photometric morphology of the cluster's horizontal branch and on estimates of its age and distance.", "doi": "10.1086/312052", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1999-06-01", "series_number": "2", "volume": "517", "issue": "2", "pages": "L135-L138" }, { "id": "authors:vr3tg-9jm49", "collection": "authors", "collection_id": "vr3tg-9jm49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190528-141732422", "type": "article", "title": "The Spectra of Main-Sequence Stars in Galactic Globular Clusters. II. CH and CN Bands in M71", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Spectra with a high signal-to-noise ratio of 79 stars that are just below the main-sequence turnoff of M71 are presented. They yield indices for the strength of the G band of CH and the ultraviolet CN band at 3885 \u00c5. These indices are each to first-order bimodal and they are anticorrelated. There are approximately equal numbers of CN-weak/CH-strong and CN-strong/CH-weak main-sequence stars in M71. It is not yet clear whether these star-to-star variations arise from primordial variations or from mixing within a fraction of individual stars as they evolve.", "doi": "10.1086/300860", "issn": "1538-3881", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1999-05", "series_number": "5", "volume": "117", "issue": "5", "pages": "2434-2439" }, { "id": "authors:khwfh-6yt02", "collection": "authors", "collection_id": "khwfh-6yt02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170408-135703580", "type": "article", "title": "The Spectra of Main-Sequence Stars in Galactic Globular Clusters. I. CH and CN Bands in M13", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Spectra with a high signal-to-noise ratio of 50 stars that are just below the main-sequence turnoff and are members of M13 are presented. They yield indices for the strength of the CH and the ultraviolet CN band. There is no evidence for a variation in the strength of either feature from star to star in this intermediate-metallicity Galactic globular cluster and, thus, no evidence for primordial variations in the abundance of C and N in M13. This supports the hypothesis that abundance variations found among the light elements in the evolved stars of M13 and commonly seen on the giant and subgiant branches of globular clusters of comparable metallicity are due primarily or entirely to mixing within a fraction of individual stars as they evolve.", "doi": "10.1086/300843", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1999-05", "series_number": "5", "volume": "117", "issue": "5", "pages": "2428-2433" }, { "id": "authors:s34q2-5p332", "collection": "authors", "collection_id": "s34q2-5p332", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190528-152102535", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. VIII. Analysis of the Field J0053+1234", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Pahre", "given_name": "Michael A.", "clpid": "Pahre-M-A" }, { "family_name": "Shopbell", "given_name": "Patrick L.", "clpid": "Shopbell-P-L" } ], "abstract": "The results of a spectroscopic investigation of a complete sample of objects with K_s<20 mag in a 2' by 7.'3 field at J005325+1234 are reported. Redshifts were successfully obtained for 163 of the 195 objects in the sample; these redshifts lie in the range [0.173, 1.44] and have a median of 0.58 (excluding 24 Galactic stars). The redshift identifications are believed to be almost complete for z<0.8. Approximately one-half of the galaxies lie in five narrow redshift features with local velocity dispersions of ~300 km s^(-1). These narrow redshift \"peaks\" are primarily populated both by absorption-line galaxies and the most luminous galaxies in the sample, although the incidence of emission lines in the luminous galaxies increases with redshift. The estimated dynamical masses of these redshift peaks, and the sky distribution of the galaxies within them, appear similar to groups or poor clusters of galaxies in the local universe at various stages of virialization. Some groups of galaxies therefore form at epochs z>1.5, and the galaxies in such groups appear to be coeval and to show little sign of ongoing star formation. The galaxies outside the redshift peaks are also clustered, albeit more weakly, are less luminous and more frequently exhibit strong emission lines. These \"isolated\" galaxies therefore appear, on average, to form stars at later epochs than the strongly clustered galaxies. The galaxy spectral energy distributions (SEDs) derived from our UBVRIK photometry are also very closely correlated with the galaxy spectral types and luminosities. These results have strong implications for the analysis of redshift surveys at intermediate redshift. The sample is used to investigate the evolution of the combined galaxy luminosity function back to z=0.8. No significant change is found in the characteristic luminosity L*, and only weak color changes are detected, consistent with passive evolution. The blue galaxy-luminosity function is more dwarf rich than the red galaxy-luminosity function. No significant change in the comoving density is found in this sample out to z~1.4, assuming that the objects without redshifts (16% of the sample) are galaxies, essentially all of which have z>0.8. This suggests that mergers are not important among the objects in this sample. A population of extremely red objects with (R-K)>5 mag exists in the infrared-selected sample; all four such objects with redshifts are found to be absorption-line galaxies with z~1. Most of the very red objects therefore appear to be galaxies with z\u22731 that are not heavily reddened by dust. A measure of the UV extinction at 2400 \u00c5 for the emission-line galaxies of a factor of 2 is obtained, implying only modest UV extinction in high-redshift star-forming galaxies.", "doi": "10.1086/306778", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1999-02-10", "series_number": "1", "volume": "512", "issue": "1", "pages": "30-47" }, { "id": "authors:yr14m-4rr97", "collection": "authors", "collection_id": "yr14m-4rr97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190528-144609335", "type": "article", "title": "B2045+265: A New Four-Image Gravitational Lens from CLASS", "author": [ { "family_name": "Fassnacht", "given_name": "C. D.", "orcid": "0000-0002-4030-5461", "clpid": "Fassnacht-C-D" }, { "family_name": "Blandford", "given_name": "R. D.", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Matthews", "given_name": "K.", "clpid": "Matthews-Keith-Astronomy" }, { "family_name": "Pearson", "given_name": "T. J.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" }, { "family_name": "Readhead", "given_name": "A. C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Womble", "given_name": "D. S.", "clpid": "Womble-D-S" }, { "family_name": "Myers", "given_name": "S. T.", "clpid": "Myers-Steven-Theodore" }, { "family_name": "Browne", "given_name": "I. W. A.", "clpid": "Browne-I-W-A" }, { "family_name": "Jackson", "given_name": "N. J.", "clpid": "Jackson-N-J" }, { "family_name": "Marlow", "given_name": "D. R.", "clpid": "Marlow-D-R" }, { "family_name": "Wilkinson", "given_name": "P. N.", "clpid": "Wilkinson-P-N" }, { "family_name": "Koopmans", "given_name": "L. V. E.", "orcid": "0000-0003-1840-0312", "clpid": "Koopmans-L-V-E" }, { "family_name": "de Bruyn", "given_name": "A. G.", "clpid": "de-Bruyn-A-G" }, { "family_name": "Schilizzi", "given_name": "R. T.", "clpid": "Schilizzi-R-T" }, { "family_name": "Bremer", "given_name": "M.", "clpid": "Bremer-M-N" }, { "family_name": "Miley", "given_name": "G.", "clpid": "Miley-G-K" } ], "abstract": "We have discovered a new gravitational lens in the Cosmic Lens All-Sky Survey (CLASS). The lens B2045+265 is a four-image system with a maximum separation of 1.\"9. A fifth radio component is detected, but its radio spectrum and its positional coincidence with infrared emission from the lensing galaxy strongly suggest that it is the radio core of the lensing galaxy. This implies that the B2045+265 lens system consists of a flat-spectrum radio source that is being lensed by another flat-spectrum radio source. Infrared images taken with the Hubble Space Telescope and the Keck I Telescope detect the lensed images of the background source and the lensing galaxy. The lensed images have relative positions and flux densities that are consistent with those seen at radio wavelengths. The lensing galaxy has magnitudes of J = 19.2, m_(F160W) = 18.8, and K = 17.6 mag in a 1.\"9 diameter aperture, which corresponds to the size of the Einstein ring of the lens. Spectra of the system taken with the Keck I Telescope reveal a lens redshift of z_l = 0.8673 and a source redshift of z_s= 1.28. The lens spectrum is typical of an Sa galaxy. The image splitting and system redshifts imply that the projected mass inside the Einstein radius of the lensing galaxy is M_E = 4.7 \u00d7 10^(11) h^(-1) M\u2299. An estimate of the light emitted inside the Einstein radius from the K magnitude gives a mass-to-light ratio in the rest-frame B band of (M/L_B)_E = 20 h (M/L_B)\u2299. Both the mass and mass-to-light ratio are higher than what is seen in nearby Sa galaxies. In fact, the implied rotation velocity for the lensing galaxy is 2\u20133 times higher than what is seen in nearby spiral galaxies. The large projected mass inside the Einstein ring radius may be the result of a significant amount of dark matter in the system, perhaps from a compact group of galaxies associated with the primary lensing galaxy; however, it may also arise from a misidentification of the source redshift. A simple model of the gravitational potential of the lens reproduces the image positions well, but further modeling is required to satisfy the constraints from the image flux density ratios. With further observations and modeling, this lens may yield an estimate of H_0.", "doi": "10.1086/300724", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1999-02", "series_number": "2", "volume": "117", "issue": "2", "pages": "658-670" }, { "id": "authors:1gr10-t9r24", "collection": "authors", "collection_id": "1gr10-t9r24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-095605206", "type": "article", "title": "Caltech Faint Galaxy Redshift Survey. VII. Data Analysis Techniques and Redshifts in the Field J0053+1234", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Pahre", "given_name": "Michael A.", "clpid": "Pahre-M-A" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Shopbell", "given_name": "Patrick L.", "clpid": "Shopbell-P-L" }, { "family_name": "Richberg", "given_name": "Kevin", "clpid": "Richberg-K" } ], "abstract": "We present the techniques used to determine redshifts and to characterize the spectra of objects in the Caltech Faint Galaxy Redshift Survey in terms of spectral classes and redshift quality classes. These are then applied to spectra from an investigation of a complete sample of objects with K_s < 20 mag in a 2 \u00d7 7.3 arcmin^2 field at J005325+1234. Redshifts were successfully obtained for 163 of the 195 objects in the sample; these redshifts lie in the range [0.173, 1.44] and have a median of 0.58 (excluding 24 Galactic stars). The sample includes two broad-lined AGNs and one QSO.", "doi": "10.1086/313184", "issn": "0067-0049", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Supplement Series", "publication_date": "1999-02", "series_number": "2", "volume": "120", "issue": "2", "pages": "171-178" }, { "id": "authors:x4g9d-qy024", "collection": "authors", "collection_id": "x4g9d-qy024", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190524-105032925", "type": "book_section", "title": "The Extremely Red Objects Found Thus Far in the Caltech Faint Galaxy Redshift Survey", "book_title": "Astrophysics with Infrared Surveys: A Prelude to SIRTF", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Pahre", "given_name": "Michael A.", "clpid": "Pahre-M-A" }, { "family_name": "Shopbell", "given_name": "Patrick L.", "clpid": "Shopbell-P-L" } ], "contributor": [ { "family_name": "Bicay", "given_name": "Michael D.", "clpid": "Bicay-M-D" }, { "family_name": "Beichman", "given_name": "C. A.", "clpid": "Beichman-C-A" }, { "family_name": "Cutri", "given_name": "Roc M.", "clpid": "Cutri-R-M" }, { "family_name": "Madore", "given_name": "Barry F.", "clpid": "Madore-B-F" } ], "abstract": "We discuss the very red objects found in the first field of the Caltech Faint Galaxy Redshift Survey, for which the observations and analysis are now complete. In this field, which is 15 arcmin^2 and at J005325+1234 there are 195 objects with K_s < 20 mag, of which 84% have redshifts. The sample includes 24 spectroscopically confirmed Galactic stars, 136 galaxies, three AGNs, and 32 objects without redshifts. \nAbout 10% of the sample has (R\u2212K) \u2265 5 mag. Four of these objects have redshifts, with 0.78 \u2264 z \u2264 1.23. Three of these are based on absorption features in the mid-UV, while the lowest redshift object shows the standard features near 4000\u00c5. Many of the objects still without redshifts have been observed spectroscopically, and no emission lines were seen in their spectra. We believe they are galaxies with z \u223c1\u22121.5 that are red due to their age and stellar content and not to some large amount of internal reddening from dust. \nAmong the many other results from this survey of interest here is a determination of the median extinction in the mid-UV for objects with strong emission line spectra at z \u223c1\u22121.3. The result is extinction by a factor of \u223c2 at 2400 \u00c5.", "doi": "10.48550/arXiv.9808343", "isbn": "9781583810019", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1999", "pages": "47-50" }, { "id": "authors:eynga-yc492", "collection": "authors", "collection_id": "eynga-yc492", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181211-082411138", "type": "book_section", "title": "Cosmological Parameters from the CERES Project", "book_title": "Cosmological Parameters and the Evolution of the Universe", "author": [ { "family_name": "Biggs", "given_name": "A.", "orcid": "0000-0002-1117-9961", "clpid": "Biggs-A-D" }, { "family_name": "Browne", "given_name": "I. W. A.", "clpid": "Browne-I-W-A" }, { "family_name": "Helbig", "given_name": "P.", "clpid": "Helbig-P" }, { "family_name": "Jackson", "given_name": "N. J.", "clpid": "Jackson-N-J" }, { "family_name": "King", "given_name": "L.", "clpid": "King-L" }, { "family_name": "Marlow", "given_name": "D. R.", "clpid": "Marlow-D-R" }, { "family_name": "McGuinness", "given_name": "A.", "clpid": "McGuinness-A" }, { "family_name": "Nair", "given_name": "S.", "clpid": "Nair-S" }, { "family_name": "Sykes", "given_name": "C. M.", "clpid": "Sykes-C-M" }, { "family_name": "Wilkinson", "given_name": "P. N.", "clpid": "Wilkinson-P-N" }, { "family_name": "Xanthopoulos", "given_name": "E.", "clpid": "Xanthopoulos-E" }, { "family_name": "de Bruyn", "given_name": "A. G.", "clpid": "de Bruyn-A-G" }, { "family_name": "Blandford", "given_name": "R.", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Cohen", "given_name": "J.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Fassnacht", "given_name": "C.", "orcid": "0000-0002-4030-5461", "clpid": "Fassnacht-C-D" }, { "family_name": "Pearson", "given_name": "T.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" }, { "family_name": "Readhead", "given_name": "A.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Womble", "given_name": "D.", "clpid": "Womble-D-S" }, { "family_name": "Bremer", "given_name": "M.", "clpid": "Bremer-M-N" }, { "family_name": "Miley", "given_name": "G.", "clpid": "Miley-G-K" }, { "family_name": "Koopmans", "given_name": "L.", "orcid": "0000-0003-1840-0312", "clpid": "Koopmans-L-V-E" }, { "family_name": "Myers", "given_name": "S.", "clpid": "Myers-Steven-Theodore" }, { "family_name": "Patnaik", "given_name": "A.", "clpid": "Patnaik-A-R" } ], "contributor": [ { "family_name": "Sato", "given_name": "Katsuhiko", "clpid": "Sato-Katsuhiko" } ], "abstract": "[no abstract]", "doi": "10.1017/s0074180900132097", "isbn": "9780792354598", "publisher": "Kluwer", "place_of_publication": "Dordrecht", "publication_date": "1999", "pages": "64" }, { "id": "authors:dhqrf-95a11", "collection": "authors", "collection_id": "dhqrf-95a11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190523-125436875", "type": "article", "title": "The complex gravitational lens system B1933+503", "author": [ { "family_name": "Sykes", "given_name": "C. M.", "clpid": "Sykes-C-M" }, { "family_name": "Browne", "given_name": "I. W. A.", "clpid": "Browne-I-W-A" }, { "family_name": "Jackson", "given_name": "N. J.", "clpid": "Jackson-N-J" }, { "family_name": "Marlow", "given_name": "D. R.", "clpid": "Marlow-D-R" }, { "family_name": "Nair", "given_name": "S.", "clpid": "Nair-S" }, { "family_name": "Wilkinson", "given_name": "P. N.", "clpid": "Wilkinson-P-N" }, { "family_name": "Blandford", "given_name": "R. D.", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Cohen", "given_name": "J.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Fassnacht", "given_name": "C. D.", "orcid": "0000-0002-4030-5461", "clpid": "Fassnacht-C-D" }, { "family_name": "Hogg", "given_name": "D.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Pearson", "given_name": "T. J.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" }, { "family_name": "Readhead", "given_name": "A. C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Womble", "given_name": "D. S.", "clpid": "Womble-D-S" }, { "family_name": "Myers", "given_name": "S. T.", "clpid": "Myers-Steven-Theodore" }, { "family_name": "de Bruyn", "given_name": "A. G.", "clpid": "de-Bruyn-A-G" }, { "family_name": "Bremer", "given_name": "M.", "clpid": "Bremer-M-N" }, { "family_name": "Miley", "given_name": "G. K.", "clpid": "Miley-G-K" }, { "family_name": "Schilizzi", "given_name": "R. T.", "clpid": "Schilizzi-R-T" } ], "abstract": "We report the discovery of the most complex arcsec-scale radio gravitational lens system yet known. B1933+503 was found during the course of the CLASS survey and MERLIN and VLA radio maps reveal up to 10 components. Four of these are compact and have flat spectra; the rest are more extended and have steep spectra. The background lensed object appears to consist of a flat-spectrum core (quadruply imaged) and two compact 'lobes' symmetrically disposed relative to the core. One of the lobes is quadruply imaged while the other is doubly imaged. An HST observation of the system with the WFPC2 shows a galaxy with an axial ratio of 0.5, but none of the images of the background object is detected. A redshift of 0.755 has been measured for the lens galaxy.", "doi": "10.1046/j.1365-8711.1998.02081.x", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "1998-12-01", "series_number": "2", "volume": "301", "issue": "2", "pages": "310-314" }, { "id": "authors:vxr1j-5b842", "collection": "authors", "collection_id": "vxr1j-5b842", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103833213", "type": "article", "title": "The O II Luminosity Density of the Universe", "author": [ { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Pahre", "given_name": "Michael A.", "clpid": "Pahre-M-A" } ], "abstract": "Equivalent widths of [O II] 3727 \u00c5 lines are measured in 375 faint galaxy spectra taken as part of the Caltech Faint Galaxy Redshift Survey centered on the Hubble Deep Field. The sensitivity of the survey spectra to the [O II] line is computed as a function of magnitude, color, and redshift. The luminosity function of galaxies in the [O II] line, and the integrated luminosity density of the universe in the [O II] line, are computed as a function of redshift. It is found that the luminosity density in the [O II] line was a factor of ~10 higher at redshifts z ~ 1 than it is at the present day. The simplest interpretation is that the star formation rate density of the universe has declined dramatically since z ~ 1.", "doi": "10.1086/306122", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1998-09-10", "series_number": "2", "volume": "504", "issue": "2", "pages": "622-628" }, { "id": "authors:0n6ps-89b17", "collection": "authors", "collection_id": "0n6ps-89b17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190604-144842812", "type": "book_section", "title": "The blue channel of the Keck low-resolution imaging spectrometer", "book_title": "Optical Astronomical Instrumentation", "author": [ { "family_name": "McCarthy", "given_name": "James K.", "clpid": "McCarthy-J-K" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Butcher", "given_name": "Brad", "clpid": "Butcher-B" }, { "family_name": "Cromer", "given_name": "John", "clpid": "Cromer-J-L" }, { "family_name": "Croner", "given_name": "Ernest", "clpid": "Croner-E-E" }, { "family_name": "Douglas", "given_name": "Bill", "clpid": "Douglas-W-R-Jr" }, { "family_name": "Goeden", "given_name": "Rich", "clpid": "Goeden-R-M" }, { "family_name": "Grewal", "given_name": "Tony", "clpid": "Grewal-T" }, { "family_name": "Lu", "given_name": "Barry", "clpid": "Lu-Barry" }, { "family_name": "Petrie", "given_name": "Hal", "clpid": "Petrie-H-L" }, { "family_name": "Weng", "given_name": "Tianxiang", "clpid": "Weng-Tianxiang" }, { "family_name": "Weber", "given_name": "Bob", "clpid": "Weber-B" }, { "family_name": "Koch", "given_name": "Donald", "clpid": "Koch-D-G" }, { "family_name": "Rodgers", "given_name": "J. Michael", "clpid": "Rodgers-J-M" } ], "contributor": [ { "family_name": "D'Odorico", "given_name": "Sandro", "clpid": "D'Odorico-S" } ], "abstract": "This paper summarizes the optical, mechanical, electrical, and software design of LRIS-B, the blue channel of the Keck Low Resolution and Imaging Spectrograph. The LRIS-B project will shortly be completing the existing LRIS instrument through the addition of dichroic beamsplitters, grisms to disperse light on the blue channel, broad-band u, B, and V photometric filters, a blue and near-UV transmitting camera lens, and a large format blue-sensitive CCD detector. LRIS-B will also introduce piezoelectric xy-actuation of the CCD detector inside its Dewar, in order to compensate for flexure in the existing instrument; ultimately the red-side CCD detector will be similarly equipped, its PZT xy-stage being independently programmed. The optical design of the LRIS-B camera uses only fused silica and calcium fluoride elements, and includes a decentered meniscus element to compensate for coma introduced by the LRIS off-axis paraboloid collimator. The design of the blue channel grisms have been optimized for maximum blaze efficiency, the highest dispersion grism having a groove density of 1200 gr/mm. Optical elements not in use at any given time will be stowed in carousels externally mounted to the instrument sidewalls. The entire instrument is designed to permit remote operation.", "doi": "10.1117/12.316831", "isbn": "9780819428028", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "1998-07-09", "pages": "81-92" }, { "id": "authors:99e2q-b9a58", "collection": "authors", "collection_id": "99e2q-b9a58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103833129", "type": "article", "title": "An Old Cluster in NGC 6822", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blakeslee", "given_name": "John P.", "clpid": "Blakeslee-J-P" } ], "abstract": "We present spectroscopy of two clusters in the dwarf irregular galaxy NGC 6822. From these we deduce an age for cluster VII of 11 ^(+4)_(-3) Gyr and [Fe/H] = -1.95 \u00b1 0.15 dex. Cluster VII appears to be an analog of the metal-poor Galactic globular clusters. Cluster VI is found to be much younger and more metal-rich, with an age of approximately 2 Gyr. Its derived metallicity, [Fe/H] \u2248 -1.0 dex, is comparable to that of the gas seen today in NGC 6822. The existence of a metal-poor old cluster in NGC 6822 rules out models for the chemical evolution of this galaxy with significant prompt initial enhancement. We find that a star formation rate that is constant with time and is within a factor of 2 of the present star formation rate can reproduce the two points on the age-metallicity relationship for NGC 6822 over the past 10 Gyr defined by these two clusters.", "doi": "10.1086/300389", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1998-06", "series_number": "6", "volume": "115", "issue": "6", "pages": "2356-2358" }, { "id": "authors:kh61v-qz121", "collection": "authors", "collection_id": "kh61v-qz121", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103833041", "type": "article", "title": "On the Existence of Jets in the Recurrent Nova T Pyxidis", "author": [ { "family_name": "O'Brien", "given_name": "T. J.", "clpid": "O'Brien-T-J" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Recently, it has been claimed that the recurrent nova T Pyxidis exhibits oppositely directed jets of ejecta apparent in features seen in H\u03b1 emission. Here we demonstrate that these features are in fact emission in the [N II] lines that lie on either side of H\u03b1 and arise from the expanding shell associated with this object rather than from collimated jets. We estimate an expansion velocity along a line of sight through the center of the shell of about 500 km s^(-1).", "doi": "10.1086/311300", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1998-05-01", "series_number": "1", "volume": "498", "issue": "1", "pages": "L59-L60" }, { "id": "authors:24jr6-7th64", "collection": "authors", "collection_id": "24jr6-7th64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832946", "type": "article", "title": "The Ages and Abundances of a Large Sample of M87 Globular Clusters", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blakeslee", "given_name": "John P.", "clpid": "Blakeslee-J-P" }, { "family_name": "Ryzhov", "given_name": "Anton", "clpid": "Ryzhov-A" } ], "abstract": "A subset of 150 globular clusters (GCs) in M87 has been selected for abundance and age determinations from the 1997 sample of Cohen & Ryzhov. This has been done solely on the basis of the signal-to-noise ratios of the spectra. Indices that measure the strength of the strongest spectral features were determined for the M87 GCs and from new data for twelve galactic GCs. Combining the new and existing data for the galactic GCs and comparing the (U-R) colors and the line indices gave qualitative indications for the ages and abundances of the M87 GC system. \n\nQuantitative results, which confirm and extend the qualitative ones, were obtained by applying the Worthey models for the integrated light of stellar systems of a single age, calibrated by observations of galactic globular clusters, to deduce abundances and ages for the objects in our sample. \n\nWe find that the M87 GCs span a wide range in metallicity, from very metal-poor to somewhat above solar metallicity. The mean [Fe/H] of -0.95 dex is higher than that of the galactic GC system, and there is a metal-rich tail that reaches to higher [Fe/H] than one finds among the galactic GCs. Excluding the very metal-rich tail, there is marginal evidence for a bimodal distribution over the single one at the 89% significance level. The two \"subpopulations\" in this model are located at -1.3 and -0.7 dex and contain 40% and 60% of the total, respectively. The dispersion in [Fe/H] for each of the model subpopulations is \u03c3 = 0.3 dex. \n\nThe mean metallicity of the M87 GC system is about a factor of 4 lower than that of the M87 stellar halo at a fixed projected radius R. The metallicity inferred from the X-ray studies is similar to that of the M87 stellar halo, not to that of the M87 GC system. \n\nWe infer the relative abundances of Na, Mg, and Fe in the M87 GCs from the strength of their spectral features. The behavior of these elements between the metal-rich and metal-poor M87 GCs is similar to that shown by the galactic GCs and by halo stars in the Galaxy. The pattern of chemical evolution in these disparate old stellar systems is, as far as we can tell, identical. \n\nSuperposed on a very large dispersion in abundance at all R, there is a small but real radial gradient in the mean abundance of the M87 GCs with R, but no detectable change in the H\u03b2 index with R. \n\nWe obtain a median age for the M87 GC system of 13 Gyr, similar to that found for the galactic GCs. The dispersion about that value (\u03c3 = 2 Gyr) is small.", "doi": "10.1086/305429", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1998-04", "series_number": "2", "volume": "496", "issue": "2", "pages": "808-826" }, { "id": "authors:ycvxp-4gw12", "collection": "authors", "collection_id": "ycvxp-4gw12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832799", "type": "article", "title": "A Blind Test of Photometric Redshift Prediction", "author": [ { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Gwyn", "given_name": "Stephen D. J.", "clpid": "Gwyn-S-D-J" }, { "family_name": "Hartwick", "given_name": "F. D. A.", "clpid": "Hartwick-F-D-A" }, { "family_name": "Mobasher", "given_name": "B.", "clpid": "Mobasher-B" }, { "family_name": "Mazzei", "given_name": "Paula", "clpid": "Mazzei-P" }, { "family_name": "Sawicki", "given_name": "Marcin", "orcid": "0000-0002-7712-7857", "clpid": "Sawicki-M" }, { "family_name": "Lin", "given_name": "Huan", "clpid": "Lin-Huan" }, { "family_name": "Yee", "given_name": "H. K. C.", "clpid": "Yee-H-K-C" }, { "family_name": "Connolly", "given_name": "Andrew J.", "clpid": "Connolly-A-J" }, { "family_name": "Brunner", "given_name": "Robert J.", "clpid": "Brunner-R-J" }, { "family_name": "Csabai", "given_name": "Istvan", "clpid": "Csabai-I" }, { "family_name": "Dickinson", "given_name": "Mark", "orcid": "0000-0001-5414-5131", "clpid": "Dickinson-Mark-E" }, { "family_name": "SubbaRao", "given_name": "Mark U.", "clpid": "SubbaRao-Mark-U" }, { "family_name": "Szalay", "given_name": "Alexander S.", "clpid": "Szalay-A-S" }, { "family_name": "Fernandez-Soto", "given_name": "Alberto", "clpid": "Fernandez-Soto-A" }, { "family_name": "Lanzetta", "given_name": "Kenneth M.", "clpid": "Lanzetta-Kenneth-M" }, { "family_name": "Yahil", "given_name": "Amos", "clpid": "Yahil-Amos" } ], "abstract": "Results of a blind test of photometric redshift predictions against spectroscopic galaxy redshifts obtained in the Hubble Deep Field with the Keck Telescope are presented. The best photometric redshift schemes predict spectroscopic redshifts with a redshift accuracy of \u0394z < 0.1 for more than 68% of sources and with \u0394z < 0.3 for 100%, when single-feature spectroscopic redshifts are removed from consideration. This test shows that photometric redshift schemes work well, at least when the photometric data are of high quality and when the sources are at moderate redshifts.", "doi": "10.1086/300277", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1998-04", "series_number": "4", "volume": "115", "issue": "4", "pages": "1418-1422" }, { "id": "authors:y4bth-5ht46", "collection": "authors", "collection_id": "y4bth-5ht46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832701", "type": "article", "title": "Keck Spectroscopy of Three Gravitational Lens Systems Discovered in the JVAS and CLASS Surveys", "author": [ { "family_name": "Fassnacht", "given_name": "Christopher D.", "orcid": "0000-0002-4030-5461", "clpid": "Fassnacht-C-D" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present spectra of three gravitational lens systems taken with the Low Resolution Imaging Spectrograph on the W. M. Keck telescopes. All of the systems were discovered in the JVAS and CLASS radio surveys, which were designed to find lenses suitable for measuring H_0. Previous spectra of these systems had low signal-to-noise ratios, and only one of the source redshifts was secure. Our observations provide unambiguous lens and source redshifts for all of the systems, with (z_l, z_s) = (0.4060, 1.339), (0.5990, 1.535), and (0.4144, 1.589) for B0712+472, B1030+074, and B1600+434, respectively. The observed image splittings in the systems imply that the masses of the lensing galaxies within their Einstein rings are 5.4 \u00d7 10^(10), 1.2 \u00d7 10^(11), and 6.3 \u00d7 10^(10) h^(-1) M_\u2299. The resulting V-band mass-to-light ratios for B0712+472 and B1030+074, measured inside their Einstein ring radii, are ~10 h (M/L)_(\u2299,V), slightly higher than values observed in nearby elliptical galaxies. For B1600+434, the mass-to-light ratio is 48 h (M/L)_(\u2299,V). This high value can be explained, at least in part, by the prominent dust lane running through the galaxy. Two of the three lens systems show evidence of variability, so monitoring may yield a time delay and thus a measurement of H_0.", "doi": "10.1086/300219", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1998-02", "series_number": "2", "volume": "115", "issue": "2", "pages": "377-382" }, { "id": "authors:9yj47-chq14", "collection": "authors", "collection_id": "9yj47-chq14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-151516596", "type": "book_section", "title": "Remote Observing with the Keck Telescope: ATM Networks and Satellite Systems", "book_title": "Astronomical Data Analysis Software and Systems VII", "author": [ { "family_name": "Shopbell", "given_name": "P. L.", "clpid": "Shopbell-P-L" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Bergman", "given_name": "L.", "clpid": "Bergman-L-A" } ], "abstract": "As a technical demonstration project for the NASA Advanced Communications Technology Satellite (ACTS), we have implemented remote observing on the 10-meter Keck II telescope on Mauna Kea from the Caltech campus in Pasadena. The data connection consists of ATM networks in Hawaii and California, running at OC-1 speeds (45 Mbit/sec), and high data rate (HDR) satellite antennae at JPL in Pasadena and Tripler Army Medical Center in Honolulu. The ACTS network is being used to enable true remote observing, as well as remote eavesdropping. The software environment is identical to that used for on-site observing at the Keck telescope, with the added benefit of the software, personnel, and other facilities provided by observing in a local environment. In this paper, we describe our high-speed remote observing network, assess the network's level of performance, and summarize the benefits and difficulties encountered in this project.", "isbn": "9781886733657", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1998", "pages": "348-351" }, { "id": "authors:7b35q-gse32", "collection": "authors", "collection_id": "7b35q-gse32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-152854352", "type": "book_section", "title": "A Progress Report on the Caltech Deep Redshift Survey", "book_title": "The Young Universe: Galaxy Formation and Evolution at Intermediate and High Redshift", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "D'Odorico", "given_name": "S.", "clpid": "D'Odorico-S" }, { "family_name": "Fontana", "given_name": "A.", "clpid": "Fontana-A" }, { "family_name": "Giallongo", "given_name": "E.", "clpid": "Giallongo-E" } ], "abstract": "The Caltech Deep Redshift Survey (CDRS) has been working\nin two fields. More than 1000 redshifts for faint field galaxies in these two fields are in hand. Our discovery of strong redshift clustering at high z is now amply confirmed by the large data set in hand. Many redshift peaks, with a typical, but non-periodic, spacing of \u2248100 h^(-1) Mpc, are seen in the HDF data. We have carried out a preliminary determination of the luminosity function for galaxies, as well as an analysis of the star formation rate as a function of time.\nThe two point correlation function for galaxies has also been derived. The spatial analysis is directly calculated using the statistics of pairs. A byproduct of this analysis is the measurement of the deviation from smooth Hubble flow (\u2248300 km/sec in the rest frame) at z \u2248 0.6. The spectral analysis is in a very preliminary state. Thus far we have established that the emission line ratios for our sample indicate photoionization by starlight and do not provide any evidence for a contribution by a harder ionizing flux (i.e. AGNs).", "isbn": "9781886733664", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1998", "pages": "420-427" }, { "id": "authors:8awy1-0v148", "collection": "authors", "collection_id": "8awy1-0v148", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-100450801", "type": "article", "title": "The External Shear Acting on Gravitational Lens B1422+231", "author": [ { "family_name": "Kundi\u0107", "given_name": "Tomislav", "clpid": "Kundi\u0107-T" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Blandford", "given_name": "Roger D.", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Lubin", "given_name": "Lori M.", "clpid": "Lubin-L-M" }, { "family_name": "Larkin", "given_name": "James E.", "orcid": "0000-0001-7687-3965", "clpid": "Larkin-J-E" } ], "abstract": "In a number of multiply imaged quasar systems, a significant contribution to the lensing potential is provided by groups and clusters of galaxies associated with the primary lens. As part of an ongoing effort to gather observational data on these systems, we present spectroscopy and near-infrared and optical photometry of galaxies in the field of the quadruple lens system B1422+231. The spectra show that the primary lens and five nearby galaxies belong to a compact group at \u03b6=0.338. The median projected radius of this group is 35h^(-1) kpc and its velocity dispersion is \u02dc550 km s^(-1). A straightforward application of the virial theorem yields a group mass of 1.4X10^(13)h^(-1) M\u2299, which provides sufficient external shear to produce the observed image configuration. This data rules out a class of models and improves the system's prospects for a measurement of the Hubble constant.", "doi": "10.1086/118647", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1997-12", "series_number": "6", "volume": "114", "issue": "6", "pages": "2276-2283" }, { "id": "authors:stn76-t6869", "collection": "authors", "collection_id": "stn76-t6869", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153225613", "type": "book_section", "title": "Remote observing with the Keck Telescope from California using NASA's ACTS satellite", "book_title": "Telescope Control Systems II", "author": [ { "family_name": "Shopbell", "given_name": "P. L.", "clpid": "Shopbell-P-L" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Bergman", "given_name": "L.", "clpid": "Bergman-L-A" } ], "contributor": [ { "family_name": "Lewis", "given_name": "Hilton", "clpid": "Lewis-H-A" } ], "abstract": "As a technical demonstration project for the NASA Advanced Communications Technology Satellite (ACTS), we have implemented remote observing on the 10-meter Keck II telescope on Mauna Kea in Hawaii from the California Institute of Technology campus in Pasadena. The data connection consists of ATM networks in Hawaii and California, running at OC-1 speeds (51 Mbit/sec) through optical fiber, and high data rate (HDR) satellite antennae at JPL in Pasadena and at the Tripler Army Medical Center in Honolulu. The ACTS network provides sufficient bandwidth to enable true remote observing, with a software environment identical to that used for on-site observing. \n\nIn this paper, we demonstrate that while the satellite link introduces a number of difficulties and decreases overall reliability of the system, remote observing is not only feasible, but provides several important advantages over standard observing paradigms. Benefits include involving more members of observing teams while decreasing expenses, enhancing real-time data analysis of observations by persons not subject to altitude-related conditions, and providing facilities, expertise, and personnel not normally available at the observing site. Although the current bandwidth of the public Internet is insufficient for true remote observing, we nevertheless anticipate a growing role for remote observing techniques, particularly as high-speed terrestrial networking paradigms, such as ATM, become more commonly available.", "doi": "10.1117/12.278835", "isbn": "9780819425348", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "1997-09-18", "pages": "209-220" }, { "id": "authors:31eg9-mag12", "collection": "authors", "collection_id": "31eg9-mag12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832596", "type": "article", "title": "The Dynamics of the M87 Globular Cluster System", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Ryzhov", "given_name": "Anton", "clpid": "Ryzhov-A" } ], "abstract": "We present the results from a study of the dynamics of the system of globular clusters around M87. After eliminating foreground galactic stars and background galaxies, we end up with a sample of 205 bona fide M87 globular clusters for which we have radial velocities determined from multislit spectra taken with the Low Resolution Imaging Spectrograph on the Keck Telescope. We find that the mean radial velocity of the M87 globular clusters agrees well with that of M87 itself and that the velocity histogram is well represented by a Gaussian distribution. We find evidence for rotation in the globular cluster system. We find that the observed velocity dispersion of the M87 globular cluster system increases with radius from 270 km s^(-1) at r = 9 kpc to \u2248 400 km s^(-1) at r = 40 kpc. The inferred mass-to-light ratio in solar units increases from 5 at r = 9 kpc to \u2248 30 at r = 40 kpc with M(r) ~ r^(1.7). The long-slit optical spectroscopy near the center of M87 and the recent analysis of the ROSAT X-ray data are in good agreement with this analysis near the nucleus and in the outer parts of M87, respectively.", "doi": "10.1086/304518", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1997-09-01", "series_number": "1", "volume": "486", "issue": "1", "pages": "230-241" }, { "id": "authors:xpxpm-4h656", "collection": "authors", "collection_id": "xpxpm-4h656", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-101258090", "type": "article", "title": "Keck Spectroscopy of the Gravitational Lens System PG 1115+080: Redshifts of the Lensing Galaxies", "author": [ { "family_name": "Kundi\u0107", "given_name": "Tomislav", "clpid": "Kundi\u0107-T" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blandford", "given_name": "Roger D.", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Lubin", "given_name": "Lori M.", "clpid": "Lubin-L-M" } ], "abstract": "The quadruple system PG 1115+080 is the second gravitational lens with a reported measurement of the Hubble constant. In addition to the primary lens, three nearby galaxies are believed to contribute significantly to the lensing potential. In this paper we report accurate redshifts for all four galaxies and show that they belong to a single group at z_d = 0.311. This group has very similar properties to Hickson's compact groups of galaxies found at lower redshifts. We briefly discuss implications for the existing lens models and derive H_0 = 52\u00b114 km s^(-1) Mpc^(-1).", "doi": "10.1086/118489", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1997-08", "series_number": "2", "volume": "114", "issue": "2", "pages": "507-510" }, { "id": "authors:n4f3b-27514", "collection": "authors", "collection_id": "n4f3b-27514", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190523-125439368", "type": "article", "title": "Counts and colours of faint galaxies in the U and R bands", "author": [ { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Pahre", "given_name": "Michael A.", "clpid": "Pahre-M-A" }, { "family_name": "McCarthy", "given_name": "James K.", "clpid": "McCarthy-J-K" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Smail", "given_name": "Ian", "orcid": "0000-0003-3037-257X", "clpid": "Smail-I" }, { "family_name": "Soifer", "given_name": "B. T.", "orcid": "0000-0002-8112-1132", "clpid": "Soifer-B-T" } ], "abstract": "Ground-based counts and colours of faint galaxies in the U and R bands in one field at high Galactic latitude are presented. Integrated over flux, a total of 1.2 \u00d7 10^5 source deg^(\u22122) are found to U = 25.5 mag and 6.3 \u00d7 10^5 source deg^(\u22122) to R = 27 mag, with d log N/dm \u223c 0.5 in the U band and d log N/dm \u223c 0.3 in the R band. Consistent with these number-magnitude curves, sources become bluer with increasing magnitude to median U\u2014 R= 0.6 mag at 24", "doi": "10.1093/mnras/288.2.404", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "1997-06-21", "series_number": "2", "volume": "288", "issue": "2", "pages": "404-410" }, { "id": "authors:qd5px-sw434", "collection": "authors", "collection_id": "qd5px-sw434", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190530-081630521", "type": "article", "title": "Faint M-Dwarfs and the Structure of the Galactic Disk", "author": [ { "family_name": "Reid", "given_name": "I. N.", "clpid": "Reid-I-N" }, { "family_name": "Gizis", "given_name": "J. E.", "orcid": "0000-0002-8916-1972", "clpid": "Gizis-J-E" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Pahre", "given_name": "M. A.", "clpid": "Pahre-M-A" }, { "family_name": "Hogg", "given_name": "D. W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Cowie", "given_name": "L.", "orcid": "0000-0002-6319-1575", "clpid": "Cowie-L-L" }, { "family_name": "Hu", "given_name": "E.", "clpid": "Hu-Esther-M" }, { "family_name": "Songaila", "given_name": "A.", "clpid": "Songaila-A" } ], "abstract": "We use broadband photometry and low-resolution spectra of a complete sample of late-K and M dwarfs brighter than I=22 in three fields at high galactic latitude to study issues relating to galactic structure and large scale abundance gradients in the Galaxy. The observed starcounts in each field are a good match to the predictions of models based on deep starcount data in other intermediate-latitude fields, and these models identify the late-type stars as members of the Galactic disk. Abundances for these late type stars are estimated via narrowband indices that measure the strength of the TiO and CaH bands in their spectra. Our results show that the average abundance in the Galactic disk remains close to solar even at heights of more than 2 kpc above the Plane.", "doi": "10.1086/133914", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1997-05", "series_number": "735", "volume": "109", "issue": "735", "pages": "559-565" }, { "id": "authors:744cw-hen02", "collection": "authors", "collection_id": "744cw-hen02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190530-082701082", "type": "article", "title": "Blue Horizontal Branch Stars in M92", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "McCarthy", "given_name": "J. K.", "clpid": "McCarthy-J-K" } ], "abstract": "We have analyzed high dispersion and high precision spectra of 5 blue horizontal branch stars in the globular cluster M92 to establish that the projected rotational velocity for these stars ranges from 15 to 40 km s^(-1). This is larger than that expected based on the rotation of their main sequence progenitors, the spin down of rotation with age, and the conservation of angular momentum. Possible explanations include a rapidly rotating stellar core. An abundance analysis of these spectra of these blue HB stars in M92 yields the same results as have been obtained from the giants in this cluster. There is a hint of a trend of higher abundance as the projected surface rotational velocity increases, which could be chance and requires confirmation.", "doi": "10.1086/118348", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1997-04", "series_number": "4", "volume": "113", "issue": "4", "pages": "1353-1358" }, { "id": "authors:2afps-55965", "collection": "authors", "collection_id": "2afps-55965", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153225522", "type": "article", "title": "Dynamical Correlations for Globular Clusters in M31", "author": [ { "family_name": "Djorgovski", "given_name": "S. G.", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-S-G" }, { "family_name": "Gal", "given_name": "R. R.", "clpid": "Gal-R-R" }, { "family_name": "McCarthy", "given_name": "J. K.", "clpid": "McCarthy-J-K" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "de Carvalho", "given_name": "R. R.", "orcid": "0000-0002-1283-3363", "clpid": "de-Carvalho-R-R" }, { "family_name": "Meylan", "given_name": "G.", "clpid": "Meylan-G" }, { "family_name": "Bendinelli", "given_name": "O.", "clpid": "Bendinelli-O" }, { "family_name": "Parmeggiani", "given_name": "G.", "clpid": "Parmeggiani-G" } ], "abstract": "We present internal velocity dispersion measurements for a set of 21 globular clusters in the Andromeda galaxy (M31). We combine them with structural and photometric cluster parameters measured earlier with the Hubble Space Telescope and from the ground to explore correlations of cluster properties and to compare them with the equivalent correlations for the Galactic globular clusters. We find that the M31 globulars follow the same correlations between velocity dispersion and luminosity, central, and average surface brightness, as do their Galactic counterparts. This suggests a common physical origin for these correlations. They may be produced by the same astrophysical conditions and processes operating at the epoch of globular cluster formation in both galaxies. The very existence of these excellent correlations, and their quantitative form as scaling laws, represent challenges and constraints for theories of globular cluster formation. Preliminary estimates of the cluster M/L ratios show correlations with the cluster metallicity, in the sense of more metal-rich clusters having lower M/L, particularly in the near-infrared. At a given metallicity, there is no detectable systematic difference between the M31 globulars and their Galactic counterparts, which suggests a great similarity of their stellar populations. The observed scatter around these trends is comparable to the expected errors, which implies a small intrinsic scatter and thus which leaves little room for possible variations in the cluster age or stellar IMF at a given metallicity.", "doi": "10.1086/310423", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1997-01-01", "series_number": "1", "volume": "474", "issue": "1", "pages": "L19-L22" }, { "id": "authors:gt6wb-4kr96", "collection": "authors", "collection_id": "gt6wb-4kr96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832491", "type": "article", "title": "Redshift Clustering in the Hubble Deep Field", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Cowie", "given_name": "Lennox L.", "orcid": "0000-0002-6319-1575", "clpid": "Cowie-L-L" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Songaila", "given_name": "Antoinette", "clpid": "Songaila-A" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Hu", "given_name": "Esther M.", "clpid": "Hu-Esther-M" }, { "family_name": "Shopbell", "given_name": "Patrick", "clpid": "Shopbell-P-L" } ], "abstract": "We present initial results from a redshift survey carried out with the low-resolution imaging spectrograph on the 10 m W. M. Keck Telescope in the Hubble Deep Field. In the redshift distribution of the 140 extragalactic objects in this sample, we find six strong peaks with velocity dispersions of ~400 km s-1. The areal density of objects within a particular peak, while it may be nonuniform, does not show evidence for strong central concentration. These peaks have characteristics (velocity dispersions, density enhancements, spacing, and spatial extent) similar to those seen in a comparable redshift survey in a different high Galactic latitude field (Cohen and coworkers), confirming that the structures are generic. They are probably the high-redshift counterparts of huge galaxy structures (\"walls\") observed locally.", "doi": "10.1086/310330", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1996-11-01", "series_number": "1", "volume": "471", "issue": "1", "pages": "L5-L9" }, { "id": "authors:ew6rs-ea752", "collection": "authors", "collection_id": "ew6rs-ea752", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190530-092729880", "type": "article", "title": "A Spectroscopic Survey for Binary Stars in the Globular Cluster NGC 5053", "author": [ { "family_name": "Yan", "given_name": "Lin", "orcid": "0000-0003-1710-9339", "clpid": "Yan-Lin" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We carried out a radial velocity survey for spectroscopic binaries in the low density globular cluster NGC 5053. Our sample contains a total of 77 cluster member giant and subgiant stars with visual magnitudes of 14.5-18.6.Of these 77 stars, 66 stars have on average of 3-4 measurements with a total of 236 velocities. A typical velocity error per measurement is \u02dc3 km s^(-1). The stars in our sample are spatially distributed from the cluster center out to 10 arcmin in radius (4.5 core radii). Among these 66 stars with multiple velocity measurements, we discovered 6 spectroscopic binary candidates. Of these six candidates, one was discovered as a binary previously by Pryor et al. (1991) and candidate ST is a binary with a very short period of three to five days. We obtained three possible orbital solutions for binary candidate ST by fitting its radial velocity data. These orbital solutions are consistent with star ST being a cluster member, although its spectrum has much stronger Mg I triplet absorption lines than that of a typical low-metallicity giant star. Using a Monte Carlo simulation method, we estimated the fraction of binary systems which may have been missed from our detection due to unfavorable orbital configurations. With our survey, the binary discovery efficiency is 29% for systems with 3 d \u2264 P \u2264 10 yr, 0.125 \u2264 q \u2264 1.75 and eccentric orbits (O \u2264 e \u2264 1). This yields a binary frequency of 29%. We also applied Kolmogorov-Smirnov (K-S) tests to the cumulative distributions of maximum velocity variations from the actual measurements and the synthetic velocity data. The results from these tests are consistent with 21 %-29% binary population with 3 d \u2264 P \u2264 10 yr, 0. 0.125 \u2264 q \u2264 1.75 in NGC 5053. The hypothesis of a binary frequency in NGC 5053 higher than 50% is rejected with a confidence level higher than 85%. The binary frequency in NGC 5053 derived from our survey is somewhat higher than estimates for other clusters by various surveys. This is perhaps related to the fact that NGC 5053 is relatively dynamically young compared to other clusters. We also argue that the binary population in globular clusters is not significantly deficient compared to binaries in other stellar environments such as open clusters, or to field and low metallicity halo stars.", "doi": "10.1086/118117", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1996-10", "series_number": "4", "volume": "112", "issue": "4", "pages": "1489-1499" }, { "id": "authors:e3esw-maw35", "collection": "authors", "collection_id": "e3esw-maw35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-104338548", "type": "article", "title": "New Insight on Galaxy Formation and Evolution From Keck Spectroscopy of the Hawaii Deep Fields", "author": [ { "family_name": "Cowie", "given_name": "Lennox L.", "orcid": "0000-0002-6319-1575", "clpid": "Cowie-L-L" }, { "family_name": "Songaila", "given_name": "Antoinette", "clpid": "Songaila-A" }, { "family_name": "Hu", "given_name": "Esther M.", "clpid": "Hu-Esther-M" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present the results of spectroscopic studies with the LRIS spectrograph on Keck of two of the Hawaii deep survey fields. The 393 objects observed cover a 26.2 arcmin^2 area and constitute a nearly complete sample down to K = 20, I = 23, and B = 24.5. The rest-frame K- band luminosity function and its evolution with redshift are described. Comparisons are made with other optically selected (B and I) samples in the literature, and the corresponding rest-frame B-band luminosity function evolution is presented. The B-band counts at B ~ 24 are shown to be a mixture of normal galaxies at modest redshifts and galaxies undergoing rapid star formation, which have a wide range of masses and which are spread over the redshift interval from z = 0.2 to beyond z = 1.7. The luminosity functions, number counts, and color distributions at optical and IR wavelengths are discussed in terms of a consistent picture of the star-forming history of the galaxy sample. [O II] emission-line diagnostics or rest-frame ultraviolet-infrared color information are used in combination with rest-frame absolute H magnitudes to construct a \"fundamental plane\" in which the evolution of the global star-formation rate with redshift can be shown, and we find that the maximum rest-frame K luminosity of galaxies undergoing rapid star formation has been declining smoothly with decreasing redshift from a value near L_* at z > 1. This smooth decrease in the characteristic luminosity of galaxies dominated by star formation can simultaneously account for the high B- band galaxy counts at faint magnitudes and the redshift distribution at z < 1 in both the B- and K-selected samples. Finally, the overall K-band light density evolution is discussed as a tracer of the baryonic mass in stars and compared with the overall rates of star formation inferred from the rest-frame ultraviolet light density as a function of redshift.", "doi": "10.1086/118058", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1996-09", "series_number": "3", "volume": "112", "issue": "3", "pages": "839-864" }, { "id": "authors:4hf2q-pss12", "collection": "authors", "collection_id": "4hf2q-pss12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832398", "type": "article", "title": "Strong Redshift Clustering of Distant Galaxies", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Pahre", "given_name": "Michael A.", "clpid": "Pahre-M-A" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" } ], "abstract": "We present initial results from a redshift survey carried out with the Low Resolution Imaging Spectrograph on the 10 m W. M. Keck Telescope of a field 14.6 arcmin^2 in solid angle. In the redshift distribution of the 106 extragalactic objects in this sample we find five strong peaks, with velocity dispersions of ~500 km s^(-1). There is evidence for a nonuniform areal density of objects in at least two peaks. These peaks have characteristics (velocity dispersions, density enhancements, spacing, and spatial extent) similar to those of nearby galaxy structures (e.g., walls and clusters), and these are expected in a survey of this kind. We suggest that the prominence of these structures in our survey relative to that in other surveys can be attributed to our K selection and dense sampling.", "doi": "10.1088/1538-4357/462/1/l9", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1996-05-01", "series_number": "1", "volume": "462", "issue": "1", "pages": "L9-L12" }, { "id": "authors:tx68z-gv578", "collection": "authors", "collection_id": "tx68z-gv578", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-145022397", "type": "book_section", "title": "A Summary of Ongoing Work at the Keck Telescope on Gravitational Lensing and on Distant Galaxies", "book_title": "Clusters, Lensing, and the Future of the Universe", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Trimble", "given_name": "Virginia", "clpid": "Trimble-V-L" }, { "family_name": "Reisenegger", "given_name": "Andreas", "clpid": "Reisenegger-A" } ], "abstract": "I present a summary of recent scientific projects relevant to the areas being discussed at this conference that have been or are in the process of being carried out at the Keck telescope by astronomers from the California Institute of Technology. Note that in most cases these are team projects, and many people are involved. Among the highlights thus far in the area of gravitational lensing are the detection of an emission line in the lens B0218+357 implying, if its identification as Mgll is correct, a redshift of 0.95, and the detection of a redshift of 0.53 for one of the arcs in the X-ray emitting cluster of galaxies MS 0440+0204. Highlights in the area of\ndistant galaxies include the deepest published optical and infrared counts, reaching to K = 24.5 mag and to R \u2248 27 mag. The first results from a redshift survey of faint field galaxies which will eventually reach to K \u2264 20 mag are also shown.", "isbn": "9781886733091", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1996", "pages": "68-75" }, { "id": "authors:e3cf0-15t24", "collection": "authors", "collection_id": "e3cf0-15t24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-150033937", "type": "book_section", "title": "A High Speed Network for Remote Observing from Caltech with the Keck Telescope", "book_title": "Astronomical Data Analysis Software and Systems V", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Bergman", "given_name": "L.", "clpid": "Bergman-L-A" }, { "family_name": "Shopbell", "given_name": "P. L.", "clpid": "Shopbell-P-L" } ], "contributor": [ { "family_name": "Jacoby", "given_name": "George H.", "clpid": "Jacoby-G-H" }, { "family_name": "Barnes", "given_name": "Jeannette", "clpid": "Barnes-J" } ], "abstract": "We are setting up a high speed (DS3) ATM network running from the dome of the 10-meter Keck Telescope on the summit of Mauna Kea in Hawaii to the Caltech campus in Pasadena, California. This network will be used to support remote observing, remote diagnostics of problems, remote software development, and other related tasks. We discuss the motivation for this effort, the network architecture, and the current status of this project.", "isbn": "978-1-58381-437-6", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1996", "pages": "376-379" }, { "id": "authors:tpbvy-p3z10", "collection": "authors", "collection_id": "tpbvy-p3z10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153225431", "type": "article", "title": "Absorption Lines in the Gravitational Lens System MG 0414+0534", "author": [ { "family_name": "Lawrence", "given_name": "C. R.", "clpid": "Lawrence-C-R" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Oke", "given_name": "J. B.", "clpid": "Oke-J-B" } ], "abstract": "Spectra of components A1 +A2 and B of the gravitational lens system MG 0414+0534 taken with the low-resolution imaging spectrograph on the Keck 10 m telescope show that the strong absorption feature seen in a low-resolution spectrum is due to a complex of Fe II lines at redshifts near that of the lensed quasar. The redshift of the lens remains unknown.", "doi": "10.1086/117714", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1995-12", "series_number": "6", "volume": "110", "issue": "6", "pages": "2583-2585" }, { "id": "authors:vnmqg-9bc34", "collection": "authors", "collection_id": "vnmqg-9bc34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153225338", "type": "article", "title": "Search for Coronal Emission Lines in Cooling Flow Clusters with the Keck 10 Meter Telescope", "author": [ { "family_name": "Yan", "given_name": "L.", "orcid": "0000-0003-1710-9339", "clpid": "Yan-Lin" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Using the Low Resolution Imaging Spectrograph on the Keck 10 m telescope, we have searched for the coronal emission line [Fe X] 6374 \u00c5 produced by the gas at temperatures of 105 106 K in the central several 10 kpc regions of two massive cooling flow clusters: Abell 1795 and PKS 0745-191. We did not detect an significant [Fe X] 6374 \u00c5 emission in either cluster. The 1 \u03c3 surface brightness limits for the [Fe X] 6374 \u00c5 line in the central 75 h^(-1)_(50) kpc region of Abell 1795 and in the central 30 h^(-1)_(50) kpc region of PKS 0745-191 are 10^(-18) ergs s^(-1) cm^(-2) arcsec^(-2) and 7 \u00d7 10^(-19) ergs s^(-1) cm^(-2) arcsec^(-2), respectively. Our upper limits of the [Fe X] 6374 \u00c5 surface brightness in both clusters are about a factor of 10 better than the previous measurements. These results are consistent with the theoretically predicted [Fe X] 6374 \u00c5 surface brightness by the popular inhomogeneous models (Sarazin & Graney 1991), in which gas cools out of the flow at a range of radii, leaving the hot gas distributed as r. The upper limits on mass cooling rate derived from our measurement are also consistent with the cooling rates derived from X-ray data for these two clusters. Our results are contradictory to the claimed significant detection in Abell 1795 by Anton et al. (1991) and the 3 \u03c3 marginal detection in PKS 0745-191 reported by Donahue & Stocke (1994). \n\nIn addition, we also measured upper limits on the [Fe X]/H\u03b1 ratio in both clusters, which provide strong constraints on various theoretical models of nebulae heating for production of the luminous low-ionization emission lines by cool (\u02dc10^4 K) nebular filaments. The [Fe X]/H\u03b1 (R < 15 kpc) ratios in Abell 1795 and PKS 0745 - 191 are less than 0.6% and 0.13%, respectively.", "doi": "10.1086/176462", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1995-11-20", "volume": "454", "pages": "44-49" }, { "id": "authors:yv7xy-40c35", "collection": "authors", "collection_id": "yv7xy-40c35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170409-080326932", "type": "article", "title": "The discovery of two giant arcs in the rich cluster A2219 with the Keck telescope", "author": [ { "family_name": "Smail", "given_name": "Ian", "orcid": "0000-0003-3037-257X", "clpid": "Smail-I" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Blandford", "given_name": "Roger", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Edge", "given_name": "Alastair C.", "clpid": "Edge-A-C" }, { "family_name": "Djorgovski", "given_name": "S. George", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-S-G" } ], "abstract": "We report the discovery with the Keck telescope of two new multiply imaged arcs in the luminous X-ray cluster A2219 (z = 0.225). The brighter arc in the field is red and we use spectroscopic and photometric information to identify it as a z ~ 1 moderately star-forming system. The brightness of this arc suggests that it is formed from two merging images of the background source, and we identify possible candidates for the third image of this source. The second giant arc in this cluster is blue and, while fainter than the red arc, it has a similarly large angular extent (32 arcsec). This arc comprises three images of a single nucleated source - the relative parities of the three images are discernible in our best-resolution images. The presence of several bright multiply imaged arcs in a single cluster allows detailed modelling of the cluster mass distribution, especially when redshift information is available. We present a lensing model of the cluster, which explains the properties of the various arcs, and we contrast this model with the optical and X-ray information available on the cluster. We uncover significant differences between the distributions of mass and X-ray gas in the cluster. We suggest that such discrepancies may indicate an on-going merger event in the cluster core, possibly associated with a group around the second brightest cluster member. The preponderance of similar merger signatures in a large fraction of the moderate-redshift clusters would indicate their dynamical immaturity.", "doi": "10.1093/mnras/277.1.1", "issn": "0035-8711", "publisher": "Royal Astronomical Society", "publication": "Monthly Notices of the Royal Astronomical Society", "publication_date": "1995-11-01", "series_number": "1", "volume": "277", "issue": "1", "pages": "1-10" }, { "id": "authors:95wzp-1ty84", "collection": "authors", "collection_id": "95wzp-1ty84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170228-093233297", "type": "article", "title": "Deep Optical Galaxy Counts with the Keck Telescope", "author": [ { "family_name": "Smail", "given_name": "Ian", "orcid": "0000-0003-3037-257X", "clpid": "Smail-I" }, { "family_name": "Hogg", "given_name": "David W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Yan", "given_name": "Lin", "orcid": "0000-0003-1710-9339", "clpid": "Yan-Lin" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present faint galaxy counts from deep VRI images obtained with the Keck Telescope. These images reach R ~ 27 in median seeing FWHM ~ 0.\"5-0.\"6, and we detect a integrated galaxy number density of 7 \u00d7 105 deg-2, equivalent to 3 \u00d7 10^(10) galaxies in the observable universe. In addition we present median galaxy colors as a function of magnitude; bluing trends are visible in all colors to R ~ 24.5. Fainter than R ~ 24.5, however, the typical V - R color becomes redder again, V - I remains constant, and R - I becomes yet bluer. These trends are consistent with the VRI count slopes, implying a decrease in the V slope at the faintest levels, which our data support. Taking advantage of our good seeing we also present median half-light radii for faint galaxies; these show a steady decline at fainter magnitudes, leading to an intrinsic half-light radius of ~0 2 for a typical R ~ 26 galaxy. Irrespective of the redshift distribution, the extremely high galaxy surface densities and their small intrinsic sizes are consistent with a scenario in which the majority of the very faint field population are dwarf galaxies or subgalactic units.", "doi": "10.1086/309647", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1995-08-20", "series_number": "2", "volume": "449", "issue": "2", "pages": "L105-L108" }, { "id": "authors:asbvt-k6715", "collection": "authors", "collection_id": "asbvt-k6715", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153225250", "type": "article", "title": "The Nonvariability of the Progenitor of Supernova 1993J in M81", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Darling", "given_name": "Jeremy", "orcid": "0000-0003-2511-2060", "clpid": "Darling-J" }, { "family_name": "Porter", "given_name": "Alain", "clpid": "Porter-A" } ], "abstract": "An archive of images taken in the early 1980s exists for a field which includes the progenitor of supernova 1993J in M81. Fifty-four CCD frames in V, and several in other colors from this set taken in 1984 are analyzed to demonstrate that the progenitor of supernova 1993J was not variable to within a limit of 0.2 mag. The frames analyzed cover a time span of 150 days. The colors of the M81 SN progenitor are consistent with those of a late G supergiant.", "doi": "10.1086/117520", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1995-07", "series_number": "1", "volume": "110", "issue": "1", "pages": "308-311" }, { "id": "authors:r0gy8-f9e64", "collection": "authors", "collection_id": "r0gy8-f9e64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170214-150501283", "type": "article", "title": "Near-infrared and optical spectroscopy of FSC 10214+4724", "author": [ { "family_name": "Soifer", "given_name": "B. T.", "orcid": "0000-0002-8112-1132", "clpid": "Soifer-B-T" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Armus", "given_name": "L.", "orcid": "0000-0003-3498-2973", "clpid": "Armus-L" }, { "family_name": "Matthews", "given_name": "K.", "clpid": "Matthews-K" }, { "family_name": "Neugebauer", "given_name": "G.", "clpid": "Neugebauer-G" }, { "family_name": "Oke", "given_name": "J. B.", "clpid": "Oke-J-B" } ], "abstract": "New infrared and optical spectroscopic observations, obtained with the W. M. Keck Telescope, are reported\nfor the highly luminous infrared source FSC 10214+4724. The rest frame optical spectrum shows new emission\nlines of [Ne III], [Ne v], [O I], [O II], [S II], and He^+, while the rest frame ultraviolet spectrum shows\nnew lines of 0 Iv] + Si IV, N III, N IV], Si II, Ne IV, and possibly N II and [Ne m], as well as clearly showing\nthat Ly\u0251 is self-absorbed. The emission-line spectrum is most characteristic of a Seyfert 2 nucleus. The preponderance of spectroscopic evidence strengthens the case for a dust-enshrouded AGN powering much or most of\nthe observed luminosity. The various spectral lines lead to a wide range in the inferred reddening and ionization\non parameter for this system, suggesting that we are viewing several environments through differing extinctions.", "doi": "10.1086/187837", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1995-04-20", "series_number": "2", "volume": "443", "issue": "2", "pages": "L65-L68" }, { "id": "authors:yh8er-11z49", "collection": "authors", "collection_id": "yh8er-11z49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153225153", "type": "article", "title": "The Keck Low-Resolution Imaging Spectrometer", "author": [ { "family_name": "Oke", "given_name": "J. B.", "clpid": "Oke-J-B" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Carr", "given_name": "M.", "clpid": "Carr-M" }, { "family_name": "Cromer", "given_name": "J.", "clpid": "Cromer-J-L" }, { "family_name": "Dingizian", "given_name": "A.", "clpid": "Dingizian-A" }, { "family_name": "Harris", "given_name": "F. H.", "clpid": "Harris-F-H" }, { "family_name": "Labrecque", "given_name": "S.", "clpid": "Labrecque-S" }, { "family_name": "Lucinio", "given_name": "R.", "clpid": "Lucinio-R" }, { "family_name": "Schaal", "given_name": "W.", "clpid": "Schaal-W-A" }, { "family_name": "Epps", "given_name": "H.", "clpid": "Epps-H" }, { "family_name": "Miller", "given_name": "J.", "clpid": "Miller-J" } ], "abstract": "The Low Resolution Imaging Spectrometer (LRIS) for the Cassegrain focus of the Keck 10-m telescope on Mauna Kea is described. It has an imaging mode so it can also be used for taking direct images. The field of view in both spectrographic and imaging modes is 6 by 7.8 arcmin. It can be used with both conventional slits and custom-punched slit masks. The optical quality of the spectrograph is good enough to take full advantage of the excellent imaging properties of the telescope itself. The detector is a cooled back-illuminated Tektronics Inc. 2048 X 2048 CCD which gives a sampling rate of 4.685 pixels per arcsec. In the spectrographic mode the spectrograph has a maximum efficiency at the peak of the grating blaze of 32%-34% for the two lowest resolution gratings and 28% for the 1200 g mm^(-1) grating. This efficiency includes the detector but not the telescope or the atmosphere.", "doi": "10.1086/133562", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1995-04", "series_number": "710", "volume": "107", "issue": "710", "pages": "375-385" }, { "id": "authors:1ppfs-kty97", "collection": "authors", "collection_id": "1ppfs-kty97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170228-140004588", "type": "article", "title": "Deep galaxy counts in the K band with the Keck telescope", "author": [ { "family_name": "Djorgovski", "given_name": "S.", "orcid": "0000-0002-0603-3087", "clpid": "Djorgovski-S-G" }, { "family_name": "Soifer", "given_name": "B. T.", "orcid": "0000-0002-8112-1132", "clpid": "Soifer-B-T" }, { "family_name": "Pahre", "given_name": "M. A.", "clpid": "Pahre-M-A" }, { "family_name": "Larkin", "given_name": "J. E.", "orcid": "0000-0001-7687-3965", "clpid": "Larkin-J-E" }, { "family_name": "Smith", "given_name": "J. D.", "orcid": "0000-0003-1545-5078", "clpid": "Smith-J-D-T" }, { "family_name": "Neugebauer", "given_name": "G.", "clpid": "Neugebauer-G" }, { "family_name": "Smail", "given_name": "I.", "orcid": "0000-0003-3037-257X", "clpid": "Smail-Ian-R" }, { "family_name": "Matthews", "given_name": "K.", "clpid": "Matthews-Keith-Astronomy" }, { "family_name": "Hogg", "given_name": "D. W.", "orcid": "0000-0003-2866-9403", "clpid": "Hogg-D-W" }, { "family_name": "Blandford", "given_name": "R. D.", "orcid": "0000-0002-1854-5506", "clpid": "Blandford-R-D" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Harrison", "given_name": "W.", "clpid": "Harrison-W" }, { "family_name": "Nelson", "given_name": "J.", "clpid": "Nelson-J" } ], "abstract": "We present deep galaxy counts in the K (\u22cb 2.2 micrometer) band, obtained at the W. M. Keck 10 m telescope. The data reach limiting magnitudes K approximately 24 mag, about 5 times deeper than the deepest published K-band images to date. The counts are performed in three small (approximately 1 min), widely separated high-latitude fields. Extensive Monte Carlo tests were used to derive the completeness corrections and minimize photometric biases. The counts continue to rise, with no sign of a turnover, down to the limits of our data, with the logarithmic slope of d log N/dm = 0.315 +/- 0.02 between K = 20 and 24 mag. This implies a cumulative surface density of approximately 5 x 10^5 galaxies/sq deg, or approximately 2 x 10^10 over the entire sky, down to K = 24 mag. Our counts are in good agreement with, although slightly lower than, those from the Hawaii Deep Survey by Cowie and collaborators; the discrepancies may be due to the small differences in the aperture corrections. We compare our counts with some of the available theoretical predictions. The data do not require models with a high value of Omega_0, but can be well fitted by models with no (or little) evolution, and cosmologies with a low value of Omega_0. Given the uncertainties in the models, it may be premature to put useful constrains on the value of Omega_0 from the counts alone. Optical-to-IR colors are computed, using CCD data obtaind previously at Palomar. We find a few red galaxies with (r-K) approximately greater than 5 mag, or (i-K) approximately greater than 5 mag; these may be ellipticals at z approximately 1. While the redshift distribution of galaxies in our counts is still unknown, the flux limits reached would allow us to detect unobscured L_* galaxies out to substantial redshifts (z greater than 3?)", "doi": "10.1086/187703", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1995-01-01", "series_number": "1", "volume": "438", "issue": "1", "pages": "L13-L16" }, { "id": "authors:z884k-c9851", "collection": "authors", "collection_id": "z884k-c9851", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153225071", "type": "article", "title": "Infrared photometry of metal rich galactic globular clusters", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Sleeper", "given_name": "Celeste", "clpid": "Sleeper-C" } ], "abstract": "Infrared photometry is presented for the giant branches of five galactic globular clusters, including three very metal rich ones located near the galactic center. New visual photometry was required for three of these objects. The metallicities of these clusters as inferred from the dereddened colors of their giant branches are in reasonable agreement with those inferred by spectroscopy of the integrated light of these systems. The spread in color seen along the giant branches of the most highly reddened of these globular clusters is shown to be consistent with patchy interstellar reddening. Abundance variations within a cluster are not required to explain the observations. The range of metallicity is confined to less than 0.2 dex in NGC 5927, and to 0.1 dex in NGC 7099. The spread in V\u2014K color is a strong constraint on abundance variations within a globular cluster.", "doi": "10.1086/117269", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1995-01", "series_number": "1", "volume": "109", "issue": "1", "pages": "242-263" }, { "id": "authors:wgfwn-nm656", "collection": "authors", "collection_id": "wgfwn-nm656", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161905051", "type": "book_section", "title": "The Globular Cluster System of M87", "book_title": "Stellar Populations", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "van der Kruit", "given_name": "P. C.", "clpid": "van-der-Kruit-P-C" }, { "family_name": "Gilmore", "given_name": "C.", "clpid": "Gilmore-C" } ], "abstract": "We have begun a program with the Low Resolution Imaging Spectrograph, operating with 30 multi-slits per exposure (Oke et al 1994, Cohen et al 1993) on the ten-meter W. M. Keck telescope located on Mauna Kea, Hawaii to observe the globular cluster systems of the Virgo ellipticals. We expect to learn about the dark matter content of galaxy halos, the formation of these halos and their cluster systems, possibly the formation of the galaxy's themselves, the interaction of the cluster system with the galaxy's gravitational potential (i.e. rotation and spinup), and the homogeneity of chemical evolution in various places. The metallicity of the globular clusters versus the metallicity of the underlying galaxy can also by analyzed. In addition the dynamics (i.e. in practice, the rotation and velocity dispersion) of the halo of the parent galaxy versus the globular cluster system can be determined.", "doi": "10.1007/978-94-011-0125-7_111", "isbn": "9780792335382", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "1995", "pages": "441-442" }, { "id": "authors:6yf0j-dn474", "collection": "authors", "collection_id": "6yf0j-dn474", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224990", "type": "article", "title": "The M31 globular cluster system: A view from the infrared", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Matthews", "given_name": "Keith", "clpid": "Matthews-Keith-Astronomy" } ], "abstract": "Infrared photometry obtained with an array detector is presented for 23 globular clusters in M31, 16 of which have projected galactocentric radii of less than 1.1 kpc. A comparison with the metallicity determined for these objects by Huchra et al [ApJ, 370, 495 (1991)] using optical spectra indicates that the errors in [Fe/H] determined optically have been underestimated. Combining our sample with previously published infrared photometry of M31 globular clusters produces a total sample of 84 objects. A comparison of the properties of the M31 globular cluster system as viewed in the infrared with that of the Milky Way globular cluster system indicates that the two are very similar. The mean metallicity of the nuclear globular clusters in the two galaxies is the same to within 0.11 dex (29%), as is the mean metallicity of the globular clusters outside the nucleus in the two galaxies, which is within the uncertainties of the two\u3008[Fe/H]\u3009determinations. Aside from a general enhancement in metallicity in the nuclear sample in M31, there is no evidence among the outer globular clusters for a spatial gradient of metallicity in the M31 globular cluster sample. This, too, is in agreement with expectations based on what is observed in the Milky Way globular cluster system.", "doi": "10.1086/117051", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1994-07", "series_number": "1", "volume": "108", "issue": "1", "pages": "128-133" }, { "id": "authors:njdyt-39638", "collection": "authors", "collection_id": "njdyt-39638", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20161019-074955837", "type": "book_section", "title": "Low-Resolution Imaging Spectrometer for the Keck Telescope", "book_title": "Instrumentation in Astronomy VIII", "author": [ { "family_name": "Oke", "given_name": "J. Beverly", "clpid": "Oke-J-B" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Carr", "given_name": "Michael M.", "clpid": "Carr-M-M" }, { "family_name": "Dingiziam", "given_name": "Arsham", "clpid": "Dingiziam-A" }, { "family_name": "Harris", "given_name": "Frederick H.", "clpid": "Harris-F-H" }, { "family_name": "Lucinio", "given_name": "Richard", "clpid": "Lucinio-R" }, { "family_name": "Labrecque", "given_name": "S.", "clpid": "Labrecque-S" }, { "family_name": "Schaal", "given_name": "W. A.", "clpid": "Schaal-W-A" }, { "family_name": "Southard", "given_name": "S., Jr.", "clpid": "Southard-S-Jr" } ], "contributor": [ { "family_name": "Crawford", "given_name": "D. I.", "clpid": "Crawford-D-I" }, { "family_name": "Craine", "given_name": "Eric R.", "clpid": "Craine-E-R" } ], "abstract": "The Low Resolution Imaging Spectrometer is designed for use at the Cassegrain focus of the Keck 10-m telescope. It provides the capability of acquiring low resolution (R equals 1000 to 5000) digital spectra, as well as 6 X 8 arc-minute moderately high spatial resolution (4.65 pixels/arc-second) direct images. Spectroscopy can be carried out with single slits which are 3 arc-minutes long. In addition punched multi-slits can also be employed which allow for the acquisition of at least forty spectra simultaneously. Since the instrument is designed to be as efficient as possible, it is a double spectrograph, with a dichroic splitting the blue and red light into separate optical paths after the collimator. Only the red side has been constructed thus far. With a 2048 by 2048 thinned Tektronix CCD as the detector the total efficiency of the red side at the peak of the grating blaze is predicted to be nearly 40%. Results of the commissioning observing runs will be described.", "doi": "10.1117/12.176745", "isbn": "0-8194-1493-X", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "1994-06-01", "pages": "178-184" }, { "id": "authors:1weqy-5h087", "collection": "authors", "collection_id": "1weqy-5h087", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224908", "type": "article", "title": "The spectrum of the brown dwarf candidate PC0025+0447", "author": [ { "family_name": "Mould", "given_name": "Jeremy", "orcid": "0000-0003-3820-1740", "clpid": "Mould-J-R" }, { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Oke", "given_name": "J. Beverly", "clpid": "Oke-J-B" }, { "family_name": "Reid", "given_name": "Neill", "clpid": "Reid-I-N" } ], "abstract": "A spectrum of the cool dwarf star PC0025+0447 obtained with the Low Resolution Imaging Spectrograph at the Keck telescope yields an upper limit on the lithium to hydrogen ratio. The limit is temperature dependent and ranges from 5 X 10^(-10) for an effective temperature of 2500 K to 1 X 10^(-10) at 1900 K. A definitive spectrum of the star's chromospheric emission is presented, but the prominence of the Balmer series is due to the weak thermal emission of the photosphere, rather than extraordinary activity. PC0025+0447 seems more likely to be a cool main sequence star than a young brown dwarf.", "doi": "10.1086/117032", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1994-06", "series_number": "6", "volume": "107", "issue": "6", "pages": "2222-2225" }, { "id": "authors:782xa-p7569", "collection": "authors", "collection_id": "782xa-p7569", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-144040919", "type": "book_section", "title": "The Software for the LRIS on the Keck 10-Meter Telescope", "book_title": "Astronomical Data Analysis Software and Systems III", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Cromer", "given_name": "J. L.", "clpid": "Cromer-J-L" }, { "family_name": "Southard", "given_name": "S., Jr.", "clpid": "Southard-S-Jr" }, { "family_name": "Clowe", "given_name": "D.", "clpid": "Clowe-D-I" } ], "contributor": [ { "family_name": "Crabtree", "given_name": "Dennis R.", "clpid": "Crabtree-D-R" }, { "family_name": "Hanisch", "given_name": "R. J.", "clpid": "Hanisch-R-J" }, { "family_name": "Barnes", "given_name": "Jeannette", "clpid": "Barnes-J" } ], "abstract": "We discuss the software for the Low Resolution and Imaging Spectrograph, one of the first light instruments built for the Keck 10-meter telescope. Details of the CCD detector readout scheme, the motor control system, the user interface, the astrometric preparatory software, etc., are given.", "isbn": "9780937707807", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1994" }, { "id": "authors:ha7jp-3c877", "collection": "authors", "collection_id": "ha7jp-3c877", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161905136", "type": "book_section", "title": "Infrared Photometry of Metal Rich Galactic Globular Clusters", "book_title": "Infrared Astronomy with Arrays: the Next Generation", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Sleeper", "given_name": "C.", "clpid": "Sleeper-C" } ], "contributor": [ { "family_name": "McLean", "given_name": "Ian S.", "clpid": "McLean-I-S" } ], "abstract": "We describe the results of a program of infrared photometry using an array detector carried out at the Las Campanas Observatory on a sample of very metal rich galactic globular clusters. We have found that the giant branches of most of these clusters show a spread in various colors which is due to patchy interstellar absorption. Strong limits can be derived on the metallicity spread within these clusters by analyzing the spread of the giant branch at a given K magnitude as a function of color used.", "doi": "10.1007/978-94-011-1070-9_20", "isbn": "9789401044660", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "1994", "pages": "93-94" }, { "id": "authors:bce12-47t86", "collection": "authors", "collection_id": "bce12-47t86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224816", "type": "article", "title": "A multi-object fiber spectrograph for The Hale Telescope", "author": [ { "family_name": "Hamilton", "given_name": "Donald", "clpid": "Hamilton-D" }, { "family_name": "Oke", "given_name": "J. B.", "clpid": "Oke-J-B" }, { "family_name": "Carr", "given_name": "M. A.", "clpid": "Carr-M-A" }, { "family_name": "Cromer", "given_name": "J.", "clpid": "Cromer-J" }, { "family_name": "Harris", "given_name": "F. H.", "clpid": "Harris-F-H" }, { "family_name": "Cohen", "given_name": "J.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Emery", "given_name": "E.", "clpid": "Emery-E" }, { "family_name": "Blake\u00e9", "given_name": "L.", "clpid": "Blake\u00e9-L" } ], "abstract": "A new faint-object spectrograph has been designed around the capabilities of fiber optics. This instrument, the Norris Spectrograph, is for exclusive use at the Cassegrain focus (f/16) of The Hale Telescope and is optimized for faint galaxy spectroscopy. There are 176 independently positionable fibers that are serially manipulated by a single robotic system. Each of these fibers sees 1.6 arcsec on the sky and the total positionable area is in excess of 300 arcmin^2. Unlike most multiobject spectrographs which utilize fibers that are several tens of meters long, the philosophy of the design of the Norris was quite the antithesis, i.e., to minimize the fiber lengths; hence, it is an entirely self-contained telescope-mounted instrument for the Cassegrain focus. The instrument consists of an integrated xy stage, for the fiber positioning, and an attached optical spectrograph. The design of the spectrograph is basically classical: spherical collimator mirror, standard reflection grating, and a newly designed all-transmissive-optics camera lens. The detector currently used is a thinned, AR-coated 2048 X 2048 Tektronix CCD. Fibers are arranged in two linear opposing banks that can access the 20 arcmin diameter field-of-view (FOV) of the instrument. The accuracy of fiber placement (assuming errorless coordinates) is less than 0.1 arcsec over the entire FOV. Fibers may be placed as close as 16 arcsec. This permits close pairings of fibers for very faint-object spectroscopy. Beam switching between paired fibers, as was done with two-channel spectrographs of yesteryear, will help average out temporal and spatial variations of the light of the night sky. Actual observations performed in this mode of operation indicate that the quality of the sky subtraction improves, as would be expected. The density of paired fibers within the Norris FOV matches the approximate density of faint field galaxies expected to a blue magnitude of 21. Software exists to take object lists (\u03b1,\u03b4) and convert them to rectilinear (x,y) values (mm) on the xy stage by gnomonic projection and to assign fibers. This software also corrects for precession of the equinoxes, proper motion if epoch differences exist, and corrects for differential atmospheric refraction. To place a single fiber takes approximately 5 s on the average. A lower limit to the efficiency of the spectrograph plus telescope has been estimated to be 6.8% at 5500 \u00c5. In order to derive the throughput of the instrument, the efficiency of the telescope, estimated to be approximately 56%, must be divided out. This value is consistent with the expectation that the reduction in efficiency from that of a standard CCD spectrograph such as The Hale Telescope's Double Spectrograph will be about a factor of 2. This results from the 60%-70% transmittance of the fibers and other losses. The spectra produced are linear with little distortion. With 10 A spectral resolution, fitting residuals on the order of 100 km s^(-1) are easily obtainable by modeling the dispersion by a third-order polynomial. The resolutions currently available range from 1 to about 20 \u00c5. The spectra have a FWHM in the direction perpendicular to that of the dispersion of about 90 \u00b5m, or equivalently about three 27 pixels found in the older Tektronix 2048 CCDs. The interorder spacing of 250 \u00b5m is large enough to permit clean spectrum extractions. The instrument has been in use for several years. The scientific programs vary from high resolution (1 \u00c5 resolution) spectroscopy of stars in nearby globular clusters to a low spectral resolution (10 \u00c5) survey of faint field galaxies. In this latter survey, with typical 2-hr exposures, absorption-line redshifts as high as z ~ 0.5 have been routinely measured. Several heretofore unknown quasars with redshifts around three have also been discovered serendipitously.", "doi": "10.1086/133312", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1993-11", "series_number": "693", "volume": "105", "issue": "693", "pages": "1308-1321" }, { "id": "authors:fn34h-q4y28", "collection": "authors", "collection_id": "fn34h-q4y28", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-140917632", "type": "book_section", "title": "Baade-Wesselink Distances to M5 and M92", "book_title": "Structure and Dynamics of Globular Clusters", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Djorgovski", "given_name": "S. G.", "clpid": "Djorgovski-S-G" }, { "family_name": "Meylan", "given_name": "Georges", "clpid": "Meylan-G" }, { "family_name": "King", "given_name": "Ivan", "clpid": "King-I-R" } ], "abstract": "A Baade-Wesselink analysis has been performed using new optical and infrared photometry of four RR Lyrae variables in the globular cluster M5 and two in M92. We obtain a distance to M5 of 6.9 \u00b1 0.45 kpc and to M92 of 7.85 \u00b1 0.45 kpc, with a 0.3 kpc additional systematic uncertainty. These results are in excellent agreement with the previously published distances, based on matching the globular cluster main sequence to that defined by the field subdwarfs of known distance.", "isbn": "9780937707692", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1993", "pages": "309-310" }, { "id": "authors:6rgpv-tgf75", "collection": "authors", "collection_id": "6rgpv-tgf75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-135701573", "type": "book_section", "title": "The M31 Globular Clusters in the Infrared", "book_title": "The Globular Cluster-Galaxy Connection", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Smith", "given_name": "Graeme H.", "clpid": "Smith-G-H" }, { "family_name": "Brodie", "given_name": "Jean P.", "clpid": "Brodie-J-P" } ], "abstract": "We review the infrared observations, both photometric and spectroscopic, of the globular clusters of M31. As a preliminary step, we summarize the observations in the infrared of individual stars in galactic globular clusters, then the observations of the integrated light of galactic globular clusters as well as the models that are used to interpret their properties. Another area that is\ndiscussed is the infrared observations of clusters in the Magellanic Clouds, their interpretation, and how they differ from galactic globular clusters. We also compare the observations of all these with the trends shown by normal elliptical galaxies.", "isbn": "9780937707678", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1993", "pages": "438-447" }, { "id": "authors:wbs0p-fnq54", "collection": "authors", "collection_id": "wbs0p-fnq54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-134324219", "type": "book_section", "title": "Baade-Wesselink Distances to MS and M92", "book_title": "The Globular Cluster-Galaxy Connection", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Smith", "given_name": "Graeme H.", "clpid": "Smith-G-H" }, { "family_name": "Brodie", "given_name": "Jean P.", "clpid": "Brodie-J-P" } ], "abstract": "A Baade-Wesselink analysis has been performed using new optical and infrared photometry of four RR Lyrae variables in the globular cluster M5 and two in M92. We obtain a distance to M5 of 6.9 \u00b1 0.45 kpc and to M92 of 7.85 \u00b1 0.45 kpc, with a 0.3 kpc additional systematic uncertainty. These results are in excellent agreement with the previously published distances, based on matching the globular cluster main sequence to that defined by the field subdwarfs of known distance.", "isbn": "9780937707678", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1993", "pages": "78-79" }, { "id": "authors:ry826-72q62", "collection": "authors", "collection_id": "ry826-72q62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224533", "type": "article", "title": "The Baade-Wesselink method applied to RR Lyrae variables in the globular clusters M5 and M92", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "An infrared Baade-Wesselink analysis is given for two RR Lyrae variables in the extremely metal-poor globular cluster M92 and four in the intermediate metallicity cluster M5. The method of analysis relies on the theoretical model atmospheres of Kurucz and on the absolute flux calibration of observed V- and K-magnitudes. The best results are obtained with V-K colors to obtain T_(eff) and K-magnitudes to deduce absolute fluxes. We obtain a distance to M5 of 6.9 \u00b1 0.45 kpc and to M92 of 7.85 \u00b1 0.45 kpc, with a 0.3 kpc additional systematic uncertainty. These results are in excellent agreement with the previously published distances, based on matching the globular cluster main sequence to that defined by the field subdwarfs of known distance. With these distances we obtain an absolute mean magnitude corrected for reddening, M^0_v, of 0.86 \u00b1 0.14 mag for the M5 RR Lyrae variables, while M^0_v= 0.62 \u00b1 0.11 for the M92 RR Lyrae variables. \n\nThe globular cluster RR Lyrae stars appear to behave just like the field RR Lyrae stars. They obey the same\u3008M_v\u3009- [Fe/H] relationship as do the field stars, and the same\u3008M_K\u3009-period relationship. Previous work which assumed the two groups of stars to behave identically is thus shown to be correct.", "doi": "10.1086/172015", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1992-12-01", "volume": "400", "pages": "528-534" }, { "id": "authors:x2tn2-gcg55", "collection": "authors", "collection_id": "x2tn2-gcg55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224615", "type": "article", "title": "Photometry of RR Lyrae variables in the globular clusters M5 and M92", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Matthews", "given_name": "K.", "clpid": "Matthews-Keith-Astronomy" } ], "abstract": "Visual photometry at V and i has been obtained for five RR Lyrae variables in the extremely metal-poor globular cluster M92 and eight in the cluster M5, of intermediate metallicity, for use in a Baade-Wesselink analysis. The periods of these variables have been updated by combining observations of the current epoch with older data from the literature. Mean magnitudes are derived from the light curves. Infrared photometry at J and has also been obtained for two RR Lyrae variables in M92 and for four variables in the cluster M5. The data were obtained with a 58 x 62 pixel InSb array. The reduction and analysis techniques are discussed. Preliminary distance determinations using the\u3008M_v\u3009 \u2014[Fe/H] relationship from the literature were derived as (m\u2014M)_0 = 14.48 \u00b1 0.04 for M92 and 14.25 \u00b1 0.05 for M5, while preliminary distance determinations using the\u3008M_K\u3009\u2014 log(P) relationship were derived as 0.15 mag smaller.", "doi": "10.1086/133109", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1992-12", "series_number": "682", "volume": "104", "issue": "682", "pages": "1205-1215" }, { "id": "authors:stx4b-0ye03", "collection": "authors", "collection_id": "stx4b-0ye03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224446", "type": "article", "title": "Giants in old open clusters - Temperatures, luminosities, and abundances from infrared photometry", "author": [ { "family_name": "Houdashelt", "given_name": "Mark L.", "clpid": "Houdashelt-M-L" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We present infrared observations for more than 100 red giants and clump stars in eight old open clusters. We have assembled the best available optical photometry for these stars and determined a consistent set of integrated physical parameters (reddening, distance modulus, abundance, and age) for the clusters. From color-color and color-magnitude diagrams that make use of both the infrared and optical data, we are able to identify quite a few stars as probable field stars rather than cluster members. However, because of a general scarcity of bright stars, it is often difficult to distinguish between cluster members on the asymptotic giant branch and field interlopers. In a ( U-V)_0, ( V-K)_0 plot, stars from the most metal-poor open clusters tend to lie between the relations defined by field and globular cluster giants. On the other hand, nearly all of the open cluster stars lie near the field giant line in a (H-K)_0 plot. The mean CO strengths of the giants in each open cluster show a range consistent with the optically determined range in [Fe/H], but the correlation between these two quantities is weak, probably because of the small total range of each and the significant uncertainties in [Fe/H]. The results for the open clusters, though, are consistent with the relation between CO and [Fe/H] established for globular clusters and considerably strengthen that relation near the solar metallicity end. For these eight open clusters, there is a modest linear correlation between [Fe/H] and age which shows a gradient in metallicity of about \u20140.1 dex per Gyr and gives [Fe/H] ~ -0.6 for \u03c4 = 5 Gyr, the age of the sun. The relation is quite similar in slope and zero point to that exhibited by clusters in the Large Magellanic Cloud. If the open cluster data are adjusted for the galactic radial metallicity gradient, the age-metallicity relation becomes intermediate to those of the Large Magellanic Cloud and the solar neighborhood. This could be an indication that the old open clusters are representative of the stellar population of the galactic thick disk. The temperatures of the cluster giant branches determined from infrared observations are tightly correlated with the optically derived values for age and [Fe/H]. Also, there is general agreement between the location of the cluster giant branches in an H-R diagram determined from infrared photometry and the predictions of the Revised Yale Isochrones. Specific differences that exist between the theoretical and semiempirical parameters can at least partially be attributed to uncertainties in the (primarily) optical data and/or the presence of convective overshooting", "doi": "10.1086/116050", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1992-01", "series_number": "1", "volume": "103", "issue": "1", "pages": "163-189" }, { "id": "authors:ephf7-1rb70", "collection": "authors", "collection_id": "ephf7-1rb70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224354", "type": "article", "title": "Abundances in the red giants of M13 and M22", "author": [ { "family_name": "Lehnert", "given_name": "M. D.", "orcid": "0000-0003-1939-5885", "clpid": "Lehnert-Matthew-D" }, { "family_name": "Bell", "given_name": "R. A.", "clpid": "Bell-R-A" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Abundances of Ca, Na, and Fe are derived for 10 red giant branch stars in the globular clusters M13 and M22, by means of model atmosphere analyses of high-dispersion spectra. It was found that M13 and M22 represent two different types of globular clusters. M13 is similar to M92 and many other globular clusters in that it displays variations in CH and CN band strengths, while showing no variation in either Ca or Fe abundance. The Na abundance was found to vary and its variation correlates with CN band strengths. This suggests that the source of the observed CN band strength variation is the same as that of the Na variation. M22, on the other hand, is similar to \u03c9 Cen, in that it displays variations in Ca, Na, and Fe abundances (\u0394[Fe/H] ~ \u0394[Ca/H] ~ 0.4) and these variations correlate with variations in CH and CN band strengths. These correlations suggest that the cause of the variations in M22 is largely \"primordial\" and mixing may only make a relatively small contribution to the C and N variations observed.", "doi": "10.1086/169648", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1991-02-01", "volume": "367", "pages": "514-523" }, { "id": "authors:d0xy1-1ww94", "collection": "authors", "collection_id": "d0xy1-1ww94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224265", "type": "article", "title": "Tests of the photometric accuracy of image restoration using the maximum entropy algorithm", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Simulations are described which test the maximum entropy image restoration algorithm as implemented in the MEMESYS3 code (version 2) of S. F. Gull and J. Skilling [Quantified Maximum Entropy, MEMSYS3 Users' Manual, version 2.0 (1989)]. It is found that at the faintest brightness levels, while the code can recover blurred point sources, they are recovered systematically too faint. The size of the photometric error depends on the brightness of the source (relative to the noise of the background) and the crowding of the field. The error increases substantially as the crowding increases. At present, the optimum technique to apply to blurred images of crowded fields where most of the sources are point sources seems to be to use a restored image to generate the list of objects, then feed this into a standard point-spread function-fitting code (such as DAOPHOT) and use this on the original blurred frame. In that manner, the most crowded fields can be analyzed without losing photometric accuracy. Additional simulations were carried out for images with the actual point spread function of the Wide Field Camera of the Hubble Space Telescope. For single isolated sources seen against a background characterized by Gaussian noise, the detection limit is degraded near its faint limit by a factor of about 4 compared to that expected. But reliable photometry cannot be obtained for sources at the detection limit in either the simulated frames, or those frames passed through the MEMSYS3 image restoration code. If one requires photometry accurate to 10%, the performance of the as-built HST plus Wide Field Camera is degraded near its faint limit by a factor of between 10 and 15 compared to that expected, even for isolated point sources.", "doi": "10.1086/115719", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1991-02", "series_number": "2", "volume": "101", "issue": "2", "pages": "734-737" }, { "id": "authors:je543-2tc62", "collection": "authors", "collection_id": "je543-2tc62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224172", "type": "article", "title": "The tidal radii of globular clusters in M31", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Freeman", "given_name": "K. C.", "clpid": "Freeman-K-C" } ], "abstract": "We have determined tidal radii for 30 globular clusters in the halo of M31 from deep direct images. Although the uncertainty of each individual measurement is large, in the mean the tidal radii suggest that the M31 globular clusters have orbital eccentricities and mass-to-light ratios that are very similar to those of galactic globular clusters.", "doi": "10.1086/115699", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1991-02", "series_number": "2", "volume": "101", "issue": "2", "pages": "483-489" }, { "id": "authors:n9b47-gvb02", "collection": "authors", "collection_id": "n9b47-gvb02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161904112", "type": "book_section", "title": "The Photometric Accuracy of Astronomical Images Restored with the MEMSYS3 Code", "book_title": "Maximum Entropy and Bayesian Methods", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Grandy", "given_name": "W. T., Jr.", "clpid": "Grandy-W-T-Jr" }, { "family_name": "Schick", "given_name": "L. H.", "clpid": "Schick-L-H" } ], "abstract": "After reviewing the causes of blur in astronomical images obtained with optical telescopes, both ground based instruments and the Hubble Space Telescope, simulations are described which test the photometric accuracy of the maximum entropy image restoration algorithm used in the code Memsys3 version 2. It is found that at the faintest brightness levels, while the code can recover blurred out point sources, they are recovered systematically too faint. The size of the photometric error depends on the brightness of the source (relative to the noise of the background) and the crowding of the field. At present, the optimum technique to apply to blurred images of crowded fields where most of the sources are point sources seems to be to use a restored image to generate the list of objects, then feed this into a standard point spread function fitting code and use this on the original blurred frame. In that manner, the most crowded fields can be analyzed without losing photometric accuracy.", "doi": "10.1007/978-94-011-3460-6_6", "isbn": "9789401055314", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "1991", "pages": "59-65" }, { "id": "authors:01c0x-xfp89", "collection": "authors", "collection_id": "01c0x-xfp89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-133424788", "type": "book_section", "title": "The tidal radii of globular clusters in M31", "book_title": "The formation and evolution of star clusters", "author": [ { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Freeman", "given_name": "Kenneth", "clpid": "Freeman-K-A" } ], "contributor": [ { "family_name": "Janes", "given_name": "Kenneth", "clpid": "Janes-K" } ], "abstract": "We have determined tidal radii for 30 globular clusters in the halo of M31 from deep direct images. Although the uncertainty of each individual measurement is large, in the mean the tidal radii suggest that the M31 globular clusters have orbital eccentricities and mass-to-light ratios that are very similar to those of Galactic globular clusters.", "isbn": "9780937707326", "publisher": "Astronomical Society of the Pacific", "place_of_publication": "San Francisco, CA", "publication_date": "1991", "pages": "377-380" }, { "id": "authors:9g9f1-ehx94", "collection": "authors", "collection_id": "9g9f1-ehx94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153224067", "type": "article", "title": "A nova-like red variable in M31", "author": [ { "family_name": "Mould", "given_name": "Jeremy", "orcid": "0000-0003-3820-1740", "clpid": "Mould-J-R" }, { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Graham", "given_name": "James R.", "clpid": "Graham-J-R" }, { "family_name": "Hamilton", "given_name": "Don", "clpid": "Hamilton-D" }, { "family_name": "Matthews", "given_name": "Keith", "clpid": "Matthews-Keith-Astronomy" }, { "family_name": "Picard", "given_name": "Alain", "clpid": "Picard-A" }, { "family_name": "Reid", "given_name": "Neill", "clpid": "Reid-I-N" }, { "family_name": "Schmidt", "given_name": "Maarten", "clpid": "Schmidt-Maarten" }, { "family_name": "Soifer", "given_name": "Tom", "orcid": "0000-0002-8112-1132", "clpid": "Soifer-B-T" }, { "family_name": "Wilson", "given_name": "Christine", "orcid": "0000-0001-5817-0991", "clpid": "Wilson-C-D" }, { "family_name": "Rich", "given_name": "R. Michael", "orcid": "0000-0003-0427-8387", "clpid": "Rich-R-M" }, { "family_name": "Gunn", "given_name": "James", "clpid": "Gunn-J-E" } ], "abstract": "A late-type supergiant which appeared in the bulge of M31 in the last observing season faded 3 bolometric magnitudes in 100 days and is now no longer detectable. It is suggested that the object was a nova of an unusual type.", "doi": "10.1086/185702", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1990-04-20", "volume": "353", "pages": "L35-L37" }, { "id": "authors:5f23w-0wk25", "collection": "authors", "collection_id": "5f23w-0wk25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-132642801", "type": "book_section", "title": "Structural Parameters for Globular Clusters in M 31", "book_title": "CCDs in Astronomy. II. New Methods and Applications of CCD Technology", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Philip", "given_name": "A. G. Davis", "clpid": "Philip-A-G-D" }, { "family_name": "Hayes", "given_name": "D. S.", "clpid": "Hayes-D-S" }, { "family_name": "Adelman", "given_name": "S. J.", "clpid": "Adelman-S-J" } ], "abstract": "After a review of existing data on structural parameters for globular clusters, we present new measurements of tidal radii for 30 globular clusters in M 31. These measurements are consistent with the globular clusters in M 31 having the same mean M/L ratio as those in the Galaxy.", "isbn": "9780933485129", "publisher": "L. Davis Press", "place_of_publication": "Schenectady, NY", "publication_date": "1990", "pages": "167-176" }, { "id": "authors:q1vwz-pcj36", "collection": "authors", "collection_id": "q1vwz-pcj36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153223981", "type": "article", "title": "The peculiar planetary nebula in M22", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Gillett", "given_name": "F. C.", "clpid": "Gillett-F-C" } ], "abstract": "The source discovered by the IRAS satellite near the center of the globular cluster M22, IRAS 18333-2357, has been studied using the IUE satellite and a ground-based optical telescope. The northern component of the close pair of stars is not a member of the cluster. The southern component is a hot star with T_(eff) \u2248 50,000 K illuminating a small planetary nebula and is a member of M22. Both the planetary nebula and its central star are extremely hydrogen deficient. The luminosity of the central star is in good agreement with that expected on theoretical grounds and with the observed luminosity of the tip of the red giant branch.", "doi": "10.1086/168061", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1989-11-15", "volume": "346", "pages": "803-807" }, { "id": "authors:58msz-cr544", "collection": "authors", "collection_id": "58msz-cr544", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170301-135108925", "type": "article", "title": "The optical/infrared counterpart(s) of IRAS 18333-2357", "author": [ { "family_name": "Gillett", "given_name": "F. C.", "clpid": "Gillett-F-C" }, { "family_name": "Jacoby", "given_name": "G. H.", "clpid": "Jacoby-G-H" }, { "family_name": "Joyce", "given_name": "R. R.", "clpid": "Joyce-R-R" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Neugebauer", "given_name": "G.", "clpid": "Neugebauer-G" }, { "family_name": "Soifer", "given_name": "B. T.", "orcid": "0000-0002-8112-1132", "clpid": "Soifer-B-T" }, { "family_name": "Nakajima", "given_name": "T.", "clpid": "Nakajima-T" }, { "family_name": "Matthews", "given_name": "K.", "clpid": "Matthews-K" } ], "abstract": "Observations of the potential optical counterparts of the unusual source IRAS 18333-2357 show that this source is associated with an extraordinary planetary nebula system in the galactic globular cluster M22. Three distinct optical objects were found within 2\" of the IRAS 18333-2357 position as determined by precisely locating the 20 \u03bcm infrared source. One object is a red star with m_v \u2248 14.7 mag, which appears to be an unrelated background field star that is possibly significantly reddened beyond the line-of-sight reddening to M22. The second stellar object is a very blue star with m_v \u2248 14.3 mag located about 1~3 south of the red star. Absorption lines of He 11 and possibly H are present in 4000-5000 A spectra of the stellar pair, similar to spectra of planetary nebula nuclei. The third member of this optical triple is an extended emission line nebulosity approximately 10\" x 7\" in size, centered about 1\" east and south of the red star. The ionized gas in this nebulosity is extraordinarily oxygen-rich and neon-rich relative to both hydrogen and helium compared to the atmospheres of M22 red giants and is substantially oxygen-rich and neon-rich relative to hydrogen in comparison with typical planetary nebulae. This nebulosity is almost certainly in M22. The blue star is also very likely to be a member of M22, the source of ionizing photons for the nebulosity and probably the luminosity source for IRAS 18333-2357. We suggest that the dust responsible for the strong infrared emission of IRAS 18333-2357 is physically associated with the M22 nebulosity. In this case the total nebular mass, comprised of 3-10 x 10^(-4) M_\u2609 of ionized gas plus > 6 x 10^(-4) M_\u2609 of silicate or carbon-based grains, is possibly dominated by the dust component. The 0, Mg, Si abundances in the case of silicate grains, or carbon in the case of carbon-based grains, may be enhanced relative to hydrogen by at least a factor of 1000 compared to solar abundances. The relative abundances and mass of the M22 nebula are very unusual among known planetary nebulae. It is speculated that this system in M22 may be the result of the interaction within a close binary system containing at least one 0-Ne white dwarf component, or perhaps related to planetary nebulae like A30 and A78.", "doi": "10.1086/167241", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1989-03-15", "series_number": "2", "volume": "338", "issue": "2", "pages": "862-874" }, { "id": "authors:mb5pv-nj384", "collection": "authors", "collection_id": "mb5pv-nj384", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-132041397", "type": "article", "title": "FIGARO, California Institute of Technology. Report for the period Jan - Dec 1988", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "FIGARO, originally written for VMS Vaxes by Keith Shortridge at the California Institute of Technology, is now maintained and distributed by Shortridge from the Anglo-Australian Observatory as part of the Starlink software library. Many additions and improvements are available in the version of FIGARO supported by the astronomy department of the California Institute of Technology. The current version of FIGARO is 2.3; distribution of version 2.4 has just begun. The unix versions of FIGARO described below are available only from Caltech.", "issn": "0002-7537", "publisher": "American Astronomical Society", "publication": "Bulletin of the Astronomical Society", "publication_date": "1989-03", "series_number": "2", "volume": "21", "issue": "2", "pages": "807" }, { "id": "authors:m9krw-1j335", "collection": "authors", "collection_id": "m9krw-1j335", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153223878", "type": "article", "title": "Slow expansion of the shell of the recurrent nova T Pyxidis and detection of a faint extended envelope", "author": [ { "family_name": "Shara", "given_name": "Michael M.", "clpid": "Shara-M-M" }, { "family_name": "Moffat", "given_name": "Anthony F. J.", "clpid": "Moffat-A-F-J" }, { "family_name": "Williams", "given_name": "Robert E.", "clpid": "Williams-R-E" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Deep CCD images of the recurrent nova T Pyx have revealed a faint, extended H\u03b1 + [N ii] halo twice as large as the previously detected shell. An [O iii] image of T Pyx shows a smooth, small shell. \n\nComparison of 1980 and 1985 images of the H\u03b1 + [N ii] shell show an expansion of less than 10%. If the bright, inner shell is due to the 1966 eruption, it should have expanded ~36% from 1980 to 1985 (assuming uniform shell expansion). We rule out the possibility of the T Pyx shell being associated with a planetary nebula-type ejection for two reasons: the shell mass is less than 10^(-4) M_\u2299, and the shell expansion velocity is ~350 km s^(-1). \n\nThis expansion velocity is much slower than the 850 km s^(-1) and 2000 km s^(-1) velocities reported by Catchpole (1969) during the 1966 outburst. \n\nIf the 10\" diameter shell is from the 1966 outburst, then the ejecta have given up most of their bulk kinetic energy by interaction with circumstellar matter or significant amounts of (now visible) low-velocity material were ejected during the last outburst, or both. The lack of strong [O i] \u03bb6300 and [S ii] \u03bb\u03bb6717,34 emission lines argues against much shock interaction at the present era, and, indirectly, for the 1944 identification of the 10\" shell, while thermonuclear runaway nova models support the multiple-velocity idea. A point-spread function subtracted from an H\u03b1 + [N ii] image of T Pyx has revealed a 2\" radius ring around the central star. This may be the ejecta from the 1966 eruption. \n\nThe photoionized shell gas implies that the central star should be UV-bright. High resolution Hubble Space Telescope imaging observations of the next T Pyx eruption might yield early detection of light echoes.", "doi": "10.1086/167143", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1989-02-15", "volume": "337", "pages": "720-729" }, { "id": "authors:y1kzj-ghx19", "collection": "authors", "collection_id": "y1kzj-ghx19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153223799", "type": "article", "title": "Blue straggler stars in the globular cluster NGC 5053", "author": [ { "family_name": "Nemec", "given_name": "James M.", "clpid": "Nemec-J-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Twenty-four blue straggler stars have been identified in the low central concentration globular cluster NGC 5053. New deep color-magnitude (C-M) diagrams to 23 mag, constructed from photometry of over 6000 stars on 4-shooter CCD frames, show that they form a well-defined sequence in the C-M diagram, extending up to ~2.2 mag brighter than the main-sequence turnoff point. The 12 most luminous blue stragglers are found to be significantly more centrally concentrated than the cluster subgiants with magnitudes in the same interval (a similar result is known for the blue stragglers in the globular cluster NGC 5466). Furthermore, they are also found to be more centrally concentrated than the 12 lower luminosity blue stragglers. Comparisons of the projected radial distributions of the bright and faint blue stragglers, with the radial distributions that are expected for stars of mass 0.8, 1.6, and 2.4 M_\u2299 (calculated using multimass King models) suggests that the brightest blue stragglers have an average mass of\u3008M\u3009= 1.3 + 0.3 M_\u2299, which is less than or comparable to twice the mean mass of a main-sequence turnoff star, and the lower luminosity blue stragglers have a mean mass similar to that of the main-sequence turnoff stars (i.e., M ~ 0.8 M_\u2299)- By fitting theoretical isochrones computed by Bell and VandenBerg to the observed main-sequence turnoff and subgiant branch regions of NGC 5053, a distance modulus of (m \u2014 M)_0 = 16.05 \u00b1 0.14 mag, and an age of 18 \u00b1 3 Gyr are derived for NGC 5053. The main-sequence luminosity function shows no sign of \" turning over \" for stars brighter than M_g ~ 5 mag.", "doi": "10.1086/167049", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1989-01-15", "volume": "336", "pages": "780-797" }, { "id": "authors:c6442-gb968", "collection": "authors", "collection_id": "c6442-gb968", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153223714", "type": "article", "title": "Atmospheric refraction effects on the Norris and Keck multiobject spectrographs", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Cromer", "given_name": "J.", "clpid": "Cromer-J" } ], "abstract": "Large field spectrographs are severely influenced by atmospheric refraction. We discuss the effect of differential refraction across the field as well as the chromatic effects for the Norris spectrograph under construction for use at Palomar Observatory and for a similar spectrograph for the Keck telescope on Mauna Kea.", "doi": "10.1086/132368", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1988-12", "series_number": "634", "volume": "100", "issue": "634", "pages": "1582-1585" }, { "id": "authors:1zpx1-6d714", "collection": "authors", "collection_id": "1zpx1-6d714", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190603-153213994", "type": "article", "title": "The globular cluster systems of the three Virgo ellipticals", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "An analysis of the systems of globular clusters around three of the brightest elliptical galaxies in the Virgo cluster (NGC 4406, NGC 4472, and NGC 4486) has been carried out with a digital detector whose field is 9 arcmin on a side. The point-source detections reach to g = 25 mag, and nearly all galaxies brighter than g \u2248 22.5 mag can be eliminated. The author finds that the colors of the globular clusters show no detectable spatial gradient, and that the median color and the distribution in color are independent of cluster luminosity and spatial position within the halo of the underlying elliptical galaxy. The median color of the Virgo globular systems is slightly redder than that of the set of globulars in the Milky Way, implying a mean metallicity difference of about a factor of 3. The magnitude distribution is not a power law, having a definite turnover at g \u2248 24.2 mag, which constrains the distance to the Virgo cluster if one believes in a universal globular cluster luminosity function. In each of the three cases, the globular cluster system has the same ellipticity and position angle as the light of the halo of the underlying galaxy, but is more extended spatially in the case of NGC 4472 and NGC 4486.", "doi": "10.1086/114667", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1988-03", "series_number": "3", "volume": "95", "issue": "3", "pages": "682-703" }, { "id": "authors:txmjr-1xk54", "collection": "authors", "collection_id": "txmjr-1xk54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161904378", "type": "book_section", "title": "The Globular Cluster System of M87", "book_title": "The Harlow-Shapley Symposium on Globular Cluster Systems in Galaxies", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Grindlay", "given_name": "Jonathan E.", "clpid": "Grindlay-J-E" }, { "family_name": "Davis Philip", "given_name": "A. G.", "clpid": "Davis-Philip-A-G" } ], "abstract": "Long exposures with the 4-Shooter at the Cassegrain focus of the 200-inch telescope at Palomar Observatory have been obtained for M87 (and two other giant ellipticals in Virgo). Ellipse fitting with a code specially developed to reject point sources has been carried out to determine the surface brightness in various bandpasses of the underlying galaxy. The color gradients in the galaxy are quite small over the entire regime between 2 and 350 arc-sec from the nucleus of M87. Also I find that there is no difference between the ellipse parameters (position angle and eccentricity) derived in the various colors, i.e. the isochromes and the isophotes coincide. Details of the study of the halo of M87 are described in a paper submitted to the Astronomical Journal.", "doi": "10.1007/978-94-015-1104-9_125", "isbn": "9789027726650", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "1988", "pages": "605-606" }, { "id": "authors:rg6hm-4zq12", "collection": "authors", "collection_id": "rg6hm-4zq12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161904470", "type": "book_section", "title": "The FIGARO Package for Astronomical Data Analysis", "book_title": "Instrumentation for Ground-Based Optical Astronomy: Present and Future", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Robinson", "given_name": "Lloyd B.", "clpid": "Robinson-L-B" } ], "abstract": "The FIGARO software package was originally written in the early 1980s by Keith Shortridge for analysis of data from Palomar Observatory. It is currently maintained by Shortridge from the Anglo-Australian Observatory. In the intervening years, FIGARO has grown rich in applications and has dispersed widely through the world from its Caltech base.", "doi": "10.1007/978-1-4612-3880-5_43", "isbn": "9781461283874", "publisher": "Springer", "place_of_publication": "New York, NY", "publication_date": "1988", "pages": "448-457" }, { "id": "authors:y86bv-4x197", "collection": "authors", "collection_id": "y86bv-4x197", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-093951608", "type": "article", "title": "Stellar Populations [Book Review]", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "In 1979 the International Astronomical Union held a colloquium on scientific research with the Space Telescope. At that time, the expected launch date was 1983; it is now late 1988 or early 1989. Stellar Populations contains the invited review papers from a meeting on that subject held at the Space Telescope Science Institute in May of 1986. This is an area of research in which the Space Telescope is sure to make great contributions and exciting discoveries. One's first impression on comparing this volume with the proceedings of the 1979 symposium (Scientific Research with the Space Telescope, U.S. Government Printing Office) is that tremendous progress has occurred within the past decade, even though astronomers have been largely limited to observations with ground-based telescopes. Because of the continuous improvement in the quantum efficiency of detectors and in the speed of computers, which in turn affects the ability of astronomers to analyze, interpret, and model their data, many of the problems outlined in 1979 have begun to be resolved.", "doi": "10.1126/science.237.4822.1626", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "1987-09-25", "series_number": "4822", "volume": "237", "issue": "4822", "pages": "1626" }, { "id": "authors:2sxf4-t2292", "collection": "authors", "collection_id": "2sxf4-t2292", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091633623", "type": "article", "title": "The distance to M5 from its RR Lyrae variables", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Gordon", "given_name": "G. A.", "clpid": "Gordon-G-A" } ], "abstract": "A variation of the Baade-Wesselink method has been applied to four RR Lyrae variables in the moderately metal-poor globular cluster M5. The method developed for the analysis utilizes an effective wavelength for each filter and relies on the accuracy of the calibration of absolute flux for bright standard stars by Oke and Gunn (1983), as well as on the accuracy of the absolute emitted fluxes predicted in the near-infrared by the Kurucz (1979) grid of model stellar atmospheres. \n\nThe results must be viewed as preliminary thus far due to apparent discrepancies between the photometrically and spectroscopically deduced angular diameter-phase relationships which are most apparent in the part of the cycle immediately following maximum light. This restricts the range of phase that can be used to derive the distance to the variables. The best value obtained for the mean of the 4 RR Lyrae stars in M5 is an absorption-corrected intensity mean absolute V magnitude of +1.05 mag (+0.15, -0.25 mag).", "doi": "10.1086/165362", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1987-07", "volume": "318", "pages": "215-231" }, { "id": "authors:561y5-9g194", "collection": "authors", "collection_id": "561y5-9g194", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091633536", "type": "article", "title": "Color gradients in three Virgo ellipticals", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Accurate surface photometry at optical wavelengths is presented for NGC 4486, NGC 4472, and NGC 4406. Ellipses of varying ellipticity and position angle as a function of semimajor axis (A) are fit over the range in A spanned by the data, 2 \u2264 A \u2264 \u2248400 arcsec. Color gradients in these galaxies are definitely present but are quite small. For each galaxy, the parameters describing the fit ellipses in the four colors are identical.", "doi": "10.1086/114235", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1986-11", "series_number": "5", "volume": "92", "issue": "5", "pages": "1039-1047" }, { "id": "authors:z4vcy-cq952", "collection": "authors", "collection_id": "z4vcy-cq952", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091633440", "type": "article", "title": "The C, N, and O abundances of giant stars in \u03c9 Centauri", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Bell", "given_name": "R. A.", "clpid": "Bell-R-A" } ], "abstract": "Indices measuring the strength of CH, C_2, CN, and NH bands and Ca ii and Ca i lines have been determined for 72 stars in \u03c9 Cen. These data, and narrow-band photometry of the 2.4 \u00b5m CO bands, are calibrated by using theoretical indices derived from synthetic spectra which are computed via a grid of model atmospheres of appropriate parameters. \n\nIn addition to the four C stars, we find two groups of giants in co Cen. Both groups include stars spanning a wide range of abundances of the heavy elements, Z. The N-enhanced stars have N/Z enhanced by a factor of 5 to 15, while both C/Z and O/Z are depleted by a factor which may be as much as 10. This depletion allows the CH and CO features to be fitted satisfactorily and yields enough nitrogen to fit CN and NH features. The N-normal stars have N/Z and C/Z within factor of 2 of solar. The range of variation of C and N is typical of those seen in other globular clusters", "doi": "10.1086/164284", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1986-06-15", "volume": "305", "pages": "698-713" }, { "id": "authors:fcjfz-ewh81", "collection": "authors", "collection_id": "fcjfz-ewh81", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091633339", "type": "article", "title": "Color-magnitude diagrams for three distant globular clusters", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Color-magnitude diagrams are presented for three distant galactic globular clusters (NGC 5466, NGC 6229, and NGC 7006). In each case the photometry reaches below the main-sequence turnoff; the ages deduced by comparison with stellar evolutionary isochrones are indistinguishable from those of the well-studied nearby clusters. The luminosity functions derived from computer-generated star counts complete to a well-defined limiting magnitude in selected fields support identical ages for the three clusters with maximum differences between NGC 5466 and NGC 6229 of 10% of the age, and between NGC 5466 and NGC 7006 of 25%. The previously published claims of an exceptionally bright turnoff for NGC 7006 are shown to be spurious. The horizontal branch of NGC 6629 is unusually red for its metallicity. Star counts and tidal radii are discussed for NGC 6229 and NGC 7006.", "doi": "10.1086/113929", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1985-11", "series_number": "11", "volume": "90", "issue": "11", "pages": "2254-2274" }, { "id": "authors:4jqdw-jf455", "collection": "authors", "collection_id": "4jqdw-jf455", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091633260", "type": "article", "title": "Nova shells. II - Calibration of the distance scale using novae", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Eight new spatially resolved nova shells have been found by imaging with a digital detector through a narrow H\u03b1 filter, and two old novae have been recovered. The 11 novae with the best determined maximum luminosities at outburst of the sample of 21 novae with reliable distances are used to derive a M_v(max)-rate of decline relationship. These 11 objects have a mean M_v 15 days past maximum of \u20145.60 \u00b1 0.45 mag. If I assume that M_v(15) is in fact constant, as is suggested by the theory, then for the full sample of 21 objects I find M_v(max, corr) = \u201410.70( \u00b10.30) + 2.41( \u00b10.23) log (t_2), where t_2 is the time in days to decline 2 mag below maximum light. Having removed all obvious sources of observational error, I deduce that the dispersion in nova outburst luminosity for a fixed rate of decline is 0.45 mag. Previously published surveys of novae in 31 are used to redetermine the distance to that galaxy.", "doi": "10.1086/163135", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1985-05-01", "volume": "292", "pages": "90-103" }, { "id": "authors:jbzx1-ftm58", "collection": "authors", "collection_id": "jbzx1-ftm58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-124044399", "type": "article", "title": "Some Faint Stars and a Bright One", "author": [ { "family_name": "Trimble", "given_name": "Virginia", "clpid": "Trimble-V-L" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "The low-luminosity stars are a wild assortment - hot and cool, old and young, dense and diffuse - almost as motley a crew as the 85 astronomers who gathered at Caltech on October 15-16, 1984 to discuss them and to honor the 75th birthday of Jesse L. Greenstein.", "issn": "0013-7812", "publisher": "California Institute of Technology", "publication": "Engineering and Science", "publication_date": "1985-03", "series_number": "4", "volume": "48", "issue": "4", "pages": "10-14" }, { "id": "authors:sjcec-ve196", "collection": "authors", "collection_id": "sjcec-ve196", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091633177", "type": "article", "title": "Interstellar CA II lines in SMC stars", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Interstellar Ca ii lines of reddened early-type stars in the SMC were observed. In addition to the component from the Milky Way, strong lines were detected at radial velocities corresponding to gas in the SMC. The interstellar Ca n lines are abnormally strong, given the small color excesses of the stars and the low metallicity of the SMC gas, which suggests that the grains contain a much smaller fraction of the interstellar calcium than they do in our galaxy. The radial velocities do not conflict with the two-galaxy model for the SMC of Matthewson and Ford (1983) if the higher-velocity system is behind the lower-velocity system.", "doi": "10.1086/113686", "issn": "0004-6256", "publisher": "American Astronomical Society", "publication": "Astronomical Journal", "publication_date": "1984-12", "series_number": "12", "volume": "89", "issue": "12", "pages": "1779-1783" }, { "id": "authors:p3k7h-xpm92", "collection": "authors", "collection_id": "p3k7h-xpm92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091633073", "type": "article", "title": "Spectrophotometry of compact embedded infrared sources in the 0.6-1.0 micron wavelength region", "author": [ { "family_name": "McGregor", "given_name": "P. J.", "clpid": "McGregor-P-J" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Spectrophotometry at 20 \u00c5 resolution in the 0.6- 1.0 \u03bcm wavelength range is presented for the compact embedded infrared sources GL 490, GL 437S, IC 1848A, GL 961, S106/IRS 3, M17/IRS 1, S235B, and M8E, for the compact H II regions GL 437W and NGC 7538/IRS 2, and for the visible objects LkH\u03b1 101, MWC 297, MWC 349, V645 Cyg, and the fan nebula associated with GL 989. The heavily obscured objects display extremely red continua, emission lines due to the Paschen series of hydrogen, and in many cases O I \u03bb8446\nand the Ca II infrared triplet lines at \u03bb\u03bb8498, 8542, and 8662, plus other weaker lines. These and other newly identified spectral characteristics of the embedded sources show similarities to those of Be stars, T Tauri stars, and to a class of emission-line stars with infrared excesses. These facts point to similar physical conditions in the circumstellar envelopes of the compact embedded sources and those of other young stellar objects that have long histories of study. \n\nEstimates of the source extinctions have been obtained from the continuum slopes in this region. Comparison of the 1 \u03bcm continuum magnitudes with estimates for the stellar photospheric fluxes based on the source luminosities suggest that scattering and circumstellar shell emission are important in forming the 1 \u03bcm continuum in several sources. The Paschen line ratios are not in general consistent with Case B recombination; this extends a conclusion deduced from the ratios of the infrared hydrogen lines Br\u03b1, Br\u03b3, and Pf\u03b3. The Paschen line decrements are qualitatively consistent with high optical depth in these lines; restrictions on possible excitation mechanisms and geometries are deduced. In those cases where they are detected, the Ca II triplet lines are equal in strength. This indicates that the optical depths in these lines are substantial. The O I \u03bb8446 line is excited by Ly\u03b2 fluorescence in most of the objects. This shows that the H I lines are excited in predominantly neutral regions and that the H\u03b1 optical depth is ~ 1000. The physical conditions in the dense, warm, and only partially ionized medium required in the embedded sources may be similar to those proposed for the broadline region of Seyfert galaxies and QSOs, but T_e is probably ~ 5000 K.", "doi": "10.1086/162636", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1984-11-15", "volume": "286", "pages": "609-629" }, { "id": "authors:dz9jw-c4m95", "collection": "authors", "collection_id": "dz9jw-c4m95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632986", "type": "article", "title": "IUE observations of the clusters of the Magellanic Clouds", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Rich", "given_name": "R. M.", "orcid": "0000-0003-0427-8387", "clpid": "Rich-R-M" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" } ], "abstract": "IUE observations of 17 clusters in the Large Magellanic Cloud are presented. The derived ultraviolet colors become progressively redder as the cluster's classification in the scheme of Searle, Wilkinson, and Bagnuolo increases. With the aid of theoretical models of the integrated light of coeval clusters of varying ages, it is shown that the SWB classification is one of increasing age accompanied by decreasing metallicity toward later SWB classes. The behavior of the UV absorption line features in the integrated light of the LMC clusters supports the contention.", "doi": "10.1086/162534", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1984-10-15", "volume": "285", "pages": "595-600" }, { "id": "authors:8ddhp-xh883", "collection": "authors", "collection_id": "8ddhp-xh883", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632901", "type": "article", "title": "The clusters of M33", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Searle", "given_name": "L.", "clpid": "Searle-L" } ], "abstract": "A selection of clusters in M33 is studied using three different observational techniques which give consistent quantitative results. M33 contains clusters which resemble galactic globular clusters as well as clusters as young as 10^8 years; the luminous clusters thus have an age range similar to those of the Magellanic Clouds rather than those of our Galaxy or M31. The four true globular clusters in our sample are all more metal poor than 47 Tuc. Based on limited data, the carbon star contribution to the integrated infrared light of the intermediate age clusters in M33 is approximately the same as in the intermediate age clusters in the Magellanic Clouds.", "doi": "10.1086/162083", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1984-06-01", "volume": "281", "pages": "141-147" }, { "id": "authors:k2zr9-tmf22", "collection": "authors", "collection_id": "k2zr9-tmf22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632810", "type": "article", "title": "Globular cluster giant branches and the metallicity scale", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" } ], "abstract": "Using the data base of Frogel, Persson, and Cohen and our earlier work, we derive characteristic parameters that describe the systematic behavior of the giants in each of 33 globular clusters. The globular cluster giant branches form a strictly homologous sequence in the H-R diagram, and their ordering correlates well with the metallicity scale published by Zinn. Nevertheless, when the giant branch parameters are used to define a metallicity ranking scheme, it appears that the Zinn abundance scale systematically underestimates the metallicity of clusters with exceptionally blue horizontal branches. \n\nThe observed luminosities of the brightest giant in each cluster agree with the theoretical core helium flash luminosity; the small dispersion of these luminosities implies that at a given metallicity the intrinsic scatter in the absolute magnitude of horizontal-branch stars is less than 0.1 mag. \n\nThe mean CO index increases as metallicity increases; analysis of the residuals from the mean relationships both of CO and of horizontal-branch type against metallicity imply that the CO abundance is unrelated to the second parameter problem. All metal-rich clusters with an adequate sample of stars show a spread in CO within each cluster comparable to that seen in 47 Tuc. Metal-poor clusters which exhibit a large star to star spread in CO are NGC 362, 2808, and 6656. \n\nThe integrated light measurements of (V - K)_0 and CO published by Aaronson and colleagues correlate with the cluster parameters determined from measurements of individual stars in a manner that can be predicted from stellar evolutionary calculations for old populations. The integrated light of such old systems, at least from V to K, is therefore well understood.", "doi": "10.1086/161573", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1983-12-15", "volume": "275", "pages": "773-789" }, { "id": "authors:r3fvq-6xz15", "collection": "authors", "collection_id": "r3fvq-6xz15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632725", "type": "article", "title": "Infrared photometry, bolometric luminosities, and effective temperatures for giant stars in 26 globular clusters", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Infrared observations of 307 giant stars in 26 globular clusters are presented. The effects of H_2O absorption on the infrared colors are examined. The color-color correlations and color-magnitude diagrams, derived using an internally consistent set of distance moduli and reddenings, identify specific clusters with problematical reddenings or low quality optical data. The mean behavior of the color-color relationships is, in all cases, in good agreement with our earlier work.", "doi": "10.1086/190906", "issn": "0067-0049", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal Supplement Series", "publication_date": "1983-11", "volume": "53", "pages": "713-749" }, { "id": "authors:0h1xm-vfn86", "collection": "authors", "collection_id": "0h1xm-vfn86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632537", "type": "article", "title": "Abundances in globular cluster red giants. V - The metal-rich globular clusters", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Low-dispersion scans of stars in eight metal-rich globular clusters are used to estimate the metallicity scale of the metal rich clusters relative to 47 Tue. Various arguments are presented which establish [Fe/H]_\u2299= \u20140.6 to \u20140.8 dex for 47 Tue. A new set of high-resolution, high-precision CCD spectra demonstrates that systematic errors have occurred in the placement of the continuum in previously published echelle analyses of metal-rich clusters. Reconciliation of analyses of low-dispersion scans and high-dispersion equivalent widths can be achieved with [Fe/H]_\u2299= \u20140.7+ 0.1 dex for 47 Tue. This value is in good agreement with Bell and Gustafsson's scale established via photometric indices computed from synthetic spectra and model atmospheres. \n\nThe metal-rich globular clusters reach the solar abundance.", "doi": "10.1086/161156", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1983-07-15", "volume": "270", "pages": "654-665" }, { "id": "authors:twpd0-k2535", "collection": "authors", "collection_id": "twpd0-k2535", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632624", "type": "article", "title": "The velocity dispersion of the globular clusters in the Fornax dwarf galaxy", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Observations of the four brightest of the globular clusters in the Fornax dwarf spheroidal galaxy yield radial velocities whose accuracy is \u00b110 km s^(-1). The observed velocity dispersion for the Fornax galaxy from this sample is too small to be detected (\u03c3 = 6 km s^(-1)). Thus, at the 95% confidence level, M/L_v is less than 8.", "doi": "10.1086/184066", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1983-07-15", "volume": "270", "pages": "L41-L42" }, { "id": "authors:6sgxy-2mj15", "collection": "authors", "collection_id": "6sgxy-2mj15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632439", "type": "article", "title": "Nova shells", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Rosenthal", "given_name": "Ann J.", "clpid": "Rosenthal-Ann-J" } ], "abstract": "A search to find spatially resolved nova shells was carried out; two new shells (around FH Ser 1970 and V533 Her 1963) were discovered. The angular sizes measured at the current epoch of the eight previously known shells around novae which erupted prior to 1945 imply that the shells are coasting out at constant velocity. Expansion velocities, interstellar absorptions, and masses of the ejected material were determined for several recent novae. A new calibration of the maximum visual luminosity-rate of decline relationship for galactic novae is given.", "doi": "10.1086/160990", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1983-05-15", "volume": "268", "pages": "689-697" }, { "id": "authors:kcr9e-pf024", "collection": "authors", "collection_id": "kcr9e-pf024", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632320", "type": "article", "title": "Photometric studies of composite stellar systems. V - Infrared photometry of star clusters in the Magellanic clouds", "author": [ { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Aaronson", "given_name": "M.", "clpid": "Aaronson-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Matthews", "given_name": "K.", "clpid": "Matthews-Keith-Astronomy" } ], "abstract": "The results of an infrared photometric study of the integrated light of 84 clusters in the Large and Small Magellanic Clouds (LMC and SMC) are presented. These clusters span nearly the complete range of cluster ages in the Clouds. In contrast to uvgr and UBV cluster colors which vary smoothly with age, the infrared colors display wide variations among the Searle, Wilkinson, and Bagnuolo groups IV-VI, i.e., in the \"intermediate age\" domain of \u02dc1-8 \u00d7 10^9 yr. Very red J - K and H - K colors for these clusters are shown to be due to the presence of luminous (M_(bol) < -4) carbon stars which are absent in the youngest and oldest clusters, and which have no effect upon the visible colors. An analysis of the CO and H - K data shows that on average half of the bolometric luminosity for 20 intermediate-age clusters comes from carbon stars on the asymptotic giant branch. This analysis agrees well with the recent carbon star surveys of Aaronson and Mould, Frogel and Cohen, and Lloyd-Evans. \n\nThe effects of luminous carbon stars upon the infrared colors of the parent clusters are strong enough that metal-poor, intermediate-age stellar populations may be detectable in the integrated light of more distant galaxies. \n\nThere is no difference, on average, between the clusters of the LMC and the SMC in the proportion of the light at 2 \u03bcm (or bolometrically) due to luminous carbon stars. This result is in apparent contrast to that of the Blanco et al. surveys of the carbon and M star populations in the general fields of the two galaxies; these surveys have revealed a sharp rise in the C/M star ratio going from the LMC to the SMC. The explanation appears to lie in the incompleteness of the Blanco et al. surveys for warm M stars in metal-poor populations. \n\nCarbon stars do not appear to be present in clusters \u2264 1 \u00d7 10^9 yr old; the infrared colors of these young clusters are dominated by M giants and supergiants which display strong CO band absorption at 2.3 \u03bcm. This lack of carbon stars agrees with the findings of Cohen et al. and Richer that a true paucity of massive, luminous (M_(bol) \u2264 -6) carbon stars exists in the general fields of the Clouds. This situation is in conflict with current theories of stellar evolution on the asymptotic giant branch. \n\nThe V - K colors of the youngest, i.e., 10^7 - 10^8 yr, clusters are compared with the single-burst model of an evolving stellar population due to Struck-Marcell and Tinsley. At a given U - V the observed V - K colors are up to 2 mag redder than the model predicts. The discrepancy is due to the neglect of red supergiants in the model; these luminous stars dominate the infrared colors and bolometric luminosities, and should be detectable in stellar populations like those in the arms of spiral galaxies. \n\nThe infrared colors of the oldest clusters of the Magellanic Clouds resemble those of globular clusters in our galaxy and in M31.", "doi": "10.1086/160763", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1983-03-01", "volume": "266", "pages": "105-129" }, { "id": "authors:hnnxn-3ts44", "collection": "authors", "collection_id": "hnnxn-3ts44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091631410", "type": "book_section", "title": "Multiple Object Fiber Optics Spectrograph Feed For The Hale Telescope", "book_title": "Instrumentation in Astronomy IV", "author": [ { "family_name": "Tubbs", "given_name": "Eldred F.", "clpid": "Tubbs-E-F" }, { "family_name": "Goss", "given_name": "Willis C.", "clpid": "Goss-W-C" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Crawford", "given_name": "David L.", "clpid": "Crawford-D-L" } ], "abstract": "A preliminary design of a fiber-optics feed for the prime-focus spectrograph of the Hale telescope using computer controlled movable fiber has been completed and a test of a proto-type configuration carried out. The complete design will divide a 76mm square field into 10 strips and will place two movable fibers in each strip. The fiber pickups, which are moved by stepper-motor driven lead screws, may be placed anywhere in the strip subject to the limitation that they not pass each other. The prototype consisted of a single strip with two fibers operated with manual input to the stepper motors. In tests performed at the 5 meter Hale telescope in April of 1981 spec-tra of two bright 0 stars (B = 8.5 mag) separated by 5 arc minutes were photographed with a 3 minute exposure using a 1200 line/mm grating and unbaked 103a0 plates. The performance of the prototype configuration was within a factor of two of the unmodified prime-focus spec-trograph indicating a potential for a ten-fold increase in the effective utilization of the telescope for spectrographic survey work when fitted with the 20-fiber feed.", "doi": "10.1117/12.933468", "isbn": "9780892523665", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "1982-11-16", "pages": "289-295" }, { "id": "authors:gqfwa-cdq64", "collection": "authors", "collection_id": "gqfwa-cdq64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632235", "type": "article", "title": "Interstellar lines in the spectra of the globular clusters around NGC 5128", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Three of the brightest globular clusters associated with the peculiar radio galaxy NGC 5128 have been observed spectroscopically. In addition to interstellar Ca II lines from our own Galaxy, two of the three show interstellar Ca II lines arising in NGC 5128. The radial velocities are not consistent with gas which shares the motion of the elliptical galaxy. In one case, the gas is possibly associated with the rotating inclined disk of gas seen close to the nucleus. The interstellar clouds are between 12 and 30 kpc from the nucleus of NGC 5128, depending on whether they are in an extension of the rotating disk and how the disk is warped.", "doi": "10.1086/183867", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1982-09-15", "volume": "260", "pages": "L45-L47" }, { "id": "authors:9808e-06r52", "collection": "authors", "collection_id": "9808e-06r52", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091632044", "type": "article", "title": "What is the second parameter - The anomalous globular cluster NGC 7006", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" } ], "abstract": "An infrared color-magnitude diagram for NGC 7006 and moderate dispersion digital optical spectra of eight of its members indicate a metal abundance of -1.5 dex with respect to the sun. However, the ratio of red to blue horizontal-branch stars is quite large and is what would be expected for a cluster of much higher metallicity. Molecular band strengths are determined for CO in four stars, and CH and CN in five stars, and it is found that none of these molecular bands are anomalously strong compared to the same molecular features in other globulars of similar metallicity but varying horizontal-branch type. This is contrary to the behavior predicted if the C, N, and O abundances are the 'second parameter' needed to explain anomalous horizontal-branch morphologies.", "doi": "10.1086/183765", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1982-04-01", "volume": "255", "pages": "L39-L43" }, { "id": "authors:sfn0g-73267", "collection": "authors", "collection_id": "sfn0g-73267", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091631963", "type": "article", "title": "The late-type stellar content of Magellanic Cloud clusters", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "New broad-band infrared photometric data have been obtained for 48 late-type giants in clusters in the Magellanic Clouds (MC). Visual spectrophotometry was obtained for a subset of these stars.\nThese observations are combined with published data for MC cluster stars and then compared with similar data for MC field giants and with predictions of various evolutionary schemes for cool,\nluminous, carbon and oxygen rich stars. \n\nThe MC cluster C stars are found to have a range in spectral energy distributions which is quite similar to that of MC field C stars. The luminosity function of the cluster C stars has a mean M_(bol) = \u20144.76 with a dispersion of \u00b10.36, also quite similar to the values for MC field C stars. However, the dispersion of the cluster C stars in M_K_0 at a given (J\u2014 K)_0 is between 2 and 3 times less than it is for the field C stars. This can arise if the present sample of clusters has a significantly smaller spread in age and/or metallicity than the progenitors of the field C stars. \n\nThe LMC field contains M giants which are redder and more luminous than any so far found in LMC or SMC clusters. This is attributed to the presence in the LMC field of a significant population of stars which are younger and/or more metal rich than the stars in the cluster sample. Differences which are found to exist between the M star populations of the LMC and the SMC clusters are also attributed to age and/or metallicity effects. \n\nIn all but one of the MC clusters which have both M and C stars, the faintest C star is brighter than the brightest M star. Such a \"transition\" luminosity appears to be correlated with the location\nof the cluster in the one-dimensional classification sequence of Searle, Wilkinson, and Bagnuolo, and it can be a useful criterion in the evaluation of theories of carbon star evolution. \n\nFinally, although the spectrophotometric data suggest that the LMC \"halo-type\" globular, NGC 1841 and 2257, have metallicities similar to one another and to that of M3, the locations of the NGC 1841 stars in a C-M diagram appear to be anomalous in the sense that its brightest stars have luminosities greater than the tips of giant branches of metal poor galactic globular clusters.", "doi": "10.1086/159660", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1982-02-15", "volume": "253", "pages": "580-592" }, { "id": "authors:hv4wv-9c719", "collection": "authors", "collection_id": "hv4wv-9c719", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091631876", "type": "article", "title": "The late-type stellar content of the Fornax and Sculptor dwarf galaxies", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Blanco", "given_name": "V. M.", "clpid": "Blanco-V-M" }, { "family_name": "McCarthy", "given_name": "M. F.", "clpid": "McCarthy-M-F" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "A field of area 0.13 square degrees has been surveyed for late-type stars in each of the Fornax and Sculptor dwarf elliptical galaxies. JHK photometric data have been obtained for most of the stars found. In Fornax, we have positively identified 25 C stars and one M giant. In Sculptor, two relatively blue C stars and a small number of possible M giants have been identified. In contrast to the Magellanic Clouds, there are no M6-M9 giants in Fornax or Sculptor. \n\nThe mean value and the variance of the bolometric luminosity function for the Fornax C stars are \u2014 4.66 \u00b1 0.47, quite similar to the values for the Magellanic Cloud C stars. The colors of the Fornax\nC stars overlap those of the C stars in the Magellanic Clouds but are bluer in the mean. The large dispersion in the color-magnitude diagram of the Fornax C stars is interpreted as arising from a significant spread in age and/or metallicity in the stellar population of Fornax. \n\nThe C stars found in Sculptor are quite similar in color and luminosity to the C stars in the globular cluster \u03c9 Centauri and are at the faint end of the luminosity distribution of C stars found in the\nMagellanic Clouds and Fornax. \n\nThe ratio of cool C stars to M stars, as determined from identical survey techniques, increases dramatically along the sequence Milky Way, LMC, SMC, and Fornax. This increase, together with systematic changes in the colors of the C and M stars, can be understood as arising from a systematic decrease in the mean metallicity of the galaxies on this sequence. The lack of concurrent significant changes in M_(bol)(mean) or M_(bol)(max) of the carbon stars may not be consistent with current theories of C star formation and evolution. \n\nThe new data for Sculptor, as well as those previously published, point to a stellar population, and possibly a star-formation history, qualitatively similar to that of \u03c9 Cen. A sharp discontinuity between Fornax and Sculptor in some of the properties which characterize the late-type stellar population of these two systems stands in contrast to a rather smooth gradation in the same properties for Fornax and galaxies more massive than it. We speculate that this discontinuity could have arisen if Sculptor were stripped of its gas component at a much earlier time than Fornax.", "doi": "10.1086/159540", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1982-01-01", "volume": "252", "pages": "133-146" }, { "id": "authors:kfe5k-8qy61", "collection": "authors", "collection_id": "kfe5k-8qy61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091631781", "type": "article", "title": "Bolometric luminosities and infrared properties of carbon stars in the Magellanic Clouds and the Galaxy", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Elias", "given_name": "Jonathan H.", "clpid": "Elias-J-H" } ], "abstract": "Broad band J, H, K photometry and narrow band CO and H_2O indices have been obtained for 89 luminous red stars in the Large Magellanic Cloud (LMC) and 21 in the Small Magellanic Cloud (SMC), chosen largely from the sample of Blanco, McCarthy, and Blanco. Most are known to be carbon stars, and their infrared properties are compared with new observations of 33 galactic carbon stars. The bolometric luminosity distributions of an unbiased sample of Magellanic Cloud carbon stars are compared with those predicted from evolutionary calculations by Renzini and Voli for double shell burning stars undergoing He shell flashes. The observed and theoretical distributions disagree markedly: nearly all the observed stars have lower luminosities than even the faintest\ntheoretical carbon star. \n\nIn addition, we find many fewer than expected high luminosity stars with initial mass greater than 3 M_\u2299. Possible explanations for this include a steep initial mass function for intermediate mass stars, a star formation rate significantly higher in the past than at present, or a neglected physical effect, such as underestimation of the importance of mass loss. Nevertheless, it appears that the hypothesis that He shell flashes lead to a dredge-up of carbon into the envelope, which results in a carbon star, can be maintained, if dredging occurs after fewer shell flashes than are predicted by presently available stellar evolutionary calculations. \n\nThe colors and indices of the late M giants in the LMC field are similar to those of late M giants in the Galaxy. \n\nThe narrow band infrared data are interpreted qualitatively in terms of the effects of molecular band absorption, which also strongly influences the infrared broad band colors of carbon stars. The small differences in the color-color relationships of the SMC and LMC samples are consistent with the differences in heavy metal abundance between the LMC, SMC, and Galaxy.", "doi": "10.1086/159308", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1981-10-15", "volume": "249", "pages": "481-503" }, { "id": "authors:d2t6z-q3074", "collection": "authors", "collection_id": "d2t6z-q3074", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091631681", "type": "article", "title": "The Giant Branch of the Globular Cluster NGC3201", "author": [ { "family_name": "Da Costa", "given_name": "G. S.", "clpid": "Da-Costa-G-S" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Infrared photometry has been obtained for 26 stars in the field of the globular cluster NGC 3201. For 14 of these stars, optical spectra have also been obtained. These observations show that the giant branch of this cluster possesses an intrinsic width of 0.13 mag (\u00b1 1 \u03c3) in (V-K)_0. We conclude however, that variable reddening across the cluster with \u03c3[E(B-V)] = 0.023 is the most likely explanation of this result. In particular, the observed intrinsic width cannot be due to a range in heavy metal abundance, since there is no star-to-star scatter in the strengths of various strong metal lines. \n\nThere is a range in G band (CH) strength at constant (V-K)_0 that correlates with CO strength: stars with weak CH also have weak CO. Comparisons with published synthetic spectra show that star-to-star variations in carbon abundance of less than a factor of 3 are sufficient to explain the range in G-band strengths. With the exception of two stars, no significant scatter was found in the strengths of the \u03bb3883 CN band. \n\nThe position of the giant branch in the infrared C-M diagram and the strengths of metal lines in the optical spectra indicate that the overall metal abundance of NGC 3201 is comparable to those of M3, M5, and NGC 6752. This is significantly more metal-poor than the preliminary abundance determined from echelle plates by Pilachowski, Sneden, and Canterna.", "doi": "10.1086/159187", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1981-09-01", "volume": "248", "pages": "612-621" }, { "id": "authors:qtr0a-s6q92", "collection": "authors", "collection_id": "qtr0a-s6q92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091631596", "type": "article", "title": "Abundances in globular cluster red giants. IV - M22 and Omega Centauri", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "A detailed abundance analysis has been performed for three members of M22 and five of \u03c9 Cen. The three giants in M22 are chemically identical with [Fe/H] = \u20141.78 dex except for a range of Na and, less certainly, Ba larger than the observational and modeling errors. The \u03c9 Cen giants show a range of abundance for all elements, with the light elements and the rare earths (plus Ba) enhanced by a larger factor than the Fe peak nuclei in the more metal-rich \u03c9 Cen stars. The two most metal-rich \u03c9 Cen stars have vastly different Na/Mg and Al/Mg ratios and Sc abundances. Explosive nucleosynthesis fails to predict the Na/Mg observed ratios at large Al/Mg values. The deduced neutron excesses are \u03b7 \u2248 10^(-2) and 5 x 10^(-4); the former is the largest known for any star. These high values of \u03b7 require massive (M \u2265 12 M_\u2299) supernova progenitors and may also produce via the s-process the strong enhancement of Ba and the rare earths seen in the metal-rich \u03c9 Cen giants. It is suggested that such massive supernovae were much rarer in the less dense halo field, leading to the observed differences in abundance patterns of globular cluster giants versus halo field dwarfs.", "doi": "10.1086/159097", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1981-08-01", "volume": "247", "pages": "869-878" }, { "id": "authors:9k073-aey55", "collection": "authors", "collection_id": "9k073-aey55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091631498", "type": "article", "title": "Infrared photometry of red giants in the globular cluster 47 Tucanae", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Infrared broad-band JHK and intermediate-band CO and R2O photometry is presented for 64 stars in the globular cluster 47 Tucanae including the long period variables (LPV) V1-4. These data are combined with optical photometric data and compared with evolutionary tracks for giant branch (GB) stars, with models for asymptotic giant branch (AGB) stars, and with determinations of CN band strengths. The main results of this paper are as follows: \n\n1. At a fixed luminosity, the 47 Tuc giants show negligible scatter in V-K or, equivalently, effective temperature. Except for the upper half-magnitude, the slope of the GB is similar to theoretical giant branch slopes of the appropriate metallicity. These two results set an upper limit of 0.2 M_\u2299 to the mass lost by stars as they evolve from the level of the horizontal branch to within 0.5 mag of the GB tip. \n\n2. Comparison of theoretical GB tracks with the observed giant branches of M92, Ml3, 47 Tuc, M7 1, and M67 show that shifts in T_(eff) are required to bring theory and observation into agreement. These shifts seem to be a function of [Fe/H] and are in the sense that the observed tracks lie progressively cooler than the theoretical tracks for higher metal abundance. This suggests that the ratio of the mixing length to the pressure scale height in the convective envelope may be a function of metallicity and/or stellar mass. \n\n3. While an independent estimate of the metallicity of 47 Tuc cannot be made from the IR data alone, the close similarity in all observed parameters of the 47 Tuc stars and the M7 1 giants studied previously implies that the two clusters must have essentially the same metallicity. \n\n4. At a given effective temperature, the CO absorption strengths of the 47 Tuc giants have a significant scatter. This scatter can be accounted for by an anticorrelation between the CO strengths and the CN strengths measured by Norris and Freeman. The origin of this anticorrelation is likely to be the effect of CN-blanketing in one of the filter band passes used to measure the CO strengths. \n\n5. At mean light the four LPVs lie sufficiently above the tip of the giant branch that they must be AGB stars. Their luminosities, temperatures, and periods are in qualitative agreement with model predictions for such stars. The periodic behavior of these variables is similar to that of Galactic LPVs. \n\n6. Stellar H_2O absorption in the band passes of the H and K filters is a strong influence on the J-H and H-K colors of some of the stars studied. Furthermore, the H_2O strengths observed in the four LPVs are greater than those in the non-LPV variables which, in turn, are greater than those in the nonvariables. Again, this is similar to the situation for cool Galactic variable and nonvariable giants.", "doi": "10.1086/158979", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1981-06-15", "volume": "246", "pages": "842-865" }, { "id": "authors:y3nkg-9yh57", "collection": "authors", "collection_id": "y3nkg-9yh57", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161904668", "type": "book_section", "title": "Observed Bolometric Luminosities of Carbon Stars", "book_title": "Physical Processes in Red Giants", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Elias", "given_name": "Jonathan H.", "clpid": "Elias-J-H" } ], "contributor": [ { "family_name": "Iben", "given_name": "Icko, Jr.", "clpid": "Iben-I-Jr" }, { "family_name": "Renzini", "given_name": "Alvio", "clpid": "Renzini-A" } ], "abstract": "To the best of our knowledge, most carbon stars are cool stars on their second ascent of the giant branch, i.e. the asymptotic giant branch. By some means they have mixed nuclear processed, carbon enriched material to their surfaces and probably have luminosities that are greater than those that mark the termination point of first time evolution up the giant branch, i.e. the location of the core helium flash. Observational and theoretical evidence for this picture may be found in Iben and Truran (1978), Renzini and Voli (1980), Scalo (1976), Richer, Olander and Westerlund (1979), and earlier references these authors cite.", "doi": "10.1007/978-94-009-8492-9_15", "isbn": "9789400984943", "publisher": "Springer Netherlands", "place_of_publication": "Dordrecht", "publication_date": "1981", "pages": "159-164" }, { "id": "authors:t4kb6-gwe37", "collection": "authors", "collection_id": "t4kb6-gwe37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161904568", "type": "book_section", "title": "Globular Cluster Giant Branches and the Helium Flash: A Comparison between Observation and Theory", "book_title": "Physical Processes in Red Giants", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Iben", "given_name": "Icko, Jr.", "clpid": "Iben-I-Jr" }, { "family_name": "Renzini", "given_name": "Alvio", "clpid": "Renzini-A" } ], "abstract": "Four years ago we began a study of globular cluster giant stars in the infrared. The first part of this program, the measurement of the 1.2\u20132.2 \u00b5m energy distributions with the use of broad band filters and the determination of the strengths of CO and H2O absorption in the stars has been published, or will soon appear in press. M3, M13, and M92 are discussed in Cohen, Frogel, and Persson (1978, hereafter CFP); M71 in Frogel, Persson, and Cohen (1979); \u03c9 Centauri in Persson et al. (1980); Pal 12 in Cohen et al. (1980); 47 Tucanae in Frogel, Persson, and Cohen (1981, hereafter FPC1); and NGC 3201 in Da Costa, Frogel, and Cohen (1981). We now have in hand similar data for 167 stars in 11 additional clusters: NGC 288, 362, 5904 (M5), 6121 (M4), 6352, 6397, 6637 (M69), 6656 (M22), 6752, 7006, and 7078 (M15) (Frogel, Persson, and Cohen 1982, hereafter FPC2). Pilachowski (1978) has also published data on several of these clusters and M10. With a rather complete sample of cluster types, we can proceed to examine how physical quantities derivable from infrared data vary from cluster to cluster. Furthermore it should be possible to establish \"benchmarks\" against which theoretical models of stellar atmospheres and evolutionary tracks can be tested.", "doi": "10.1007/978-94-009-8492-9_6", "isbn": "9789400984943", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "1981", "pages": "55-62" }, { "id": "authors:280sp-q0h19", "collection": "authors", "collection_id": "280sp-q0h19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091630742", "type": "article", "title": "Abundances in globular cluster red giants. III - M71, M67, and NGC 2420", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "High-dispersion spectra of four stars in the metal-rich globular cluster M71, four giants in the old open cluster M67, and two members of the metal-poor old open cluster NGC 2420 are analyzed with the aid of model atmospheres. The derived abundances are Fe/H = -1.27, -0.39, and -0.61 dex with regard to the sun for M71, M67, and NGC 2420, respectively. The pattern of elemental abundances is very similar over the full range from M92 to M67, with the most obvious differences being the strong overdepletion of copper, and perhaps scandium, with progressively lower metallicities. The metallicity derived for M71 is much lower than previous estimates, and the consequences of this for the abundance scale of globular clusters and the formation of the halo and disk of the Galaxy are discussed.", "doi": "10.1086/158412", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1980-11-01", "volume": "241", "pages": "981-1000" }, { "id": "authors:z0s47-rre96", "collection": "authors", "collection_id": "z0s47-rre96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091630652", "type": "article", "title": "Photometric studies of composite stellar systems. IV - Infrared photometry of globular clusters in M31 and a comparison with early-type galaxies", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "The results of an infrared photometric investigation of 40 globular clusters in and around M31 are presented. The (V - K)_0 colors of the M31 globulars are tightly correlated with other broadband colors and with reddening-free metallicity parameters derived from optical spectrophotometry by Searle. Over a range of \u02dc1.2 mag in (V - K)_0, the scatter is consistent with observational error. Thus the 0.3-2.2 \u03bcm energy distributions are uniquely predicted by the metallicity and vice versa. A comparison of the (V - K)0 colors with those of galactic globulars allows an independent derivation of the metallicities of individual M31 globulars. \n\nThe broad-band infrared data are compared with predictions from integrated light models based on the Ciardullo and Demarque isochrones. The agreement is quite good for models with an initial mass function of slope \u2272 the Salpeter value independent of metallicity, thus ruling out the possibility that a late-type dwarf component is making a significant contribution to the infrared light. CO and H_2O indices measured for eight and seven of the clusters, respectively, give the same result. \n\nEarly-type galaxies are seen to have much redder broad-band colors and stronger CO and H_2O indices than the most metal-rich M31 or galactic globular observed. Compared to the reddest globular clusters, at a given (U - V)_0 early-type galaxies are on average 0.3 mag redder in (V - K)_0. Although the stellar synthesis models reproduce cluster broad-band colors reasonably well, they do not reproduce the U - V/ V - K distribution of early-type galaxies. We propose that the early-type galaxies contain a population of cool luminous stars present neither in the clusters nor in the stellar synthesis models. One candidate for this population is a giant branch of stars considerably more metal rich than the Sun. More interesting is the possibility that there is a contribution to the integrated infrared light from asymptotic giant-branch stars above the first red giant tip. Such stars could be of intermediate age. \n\nThe luminosity functions for the M31 and the galactic globulars are examined with the aid of models to investigate the possibility that metal-enhanced star formation or variations in the initial mass function can be detected in integrated light. \n\nTwo appendices present new infrared data for a faint dE galaxy in the Virgo cluster, and a recalibration of the integrated light models presented by Aaron son et al..", "doi": "10.1086/158291", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1980-09-15", "volume": "240", "pages": "785-802" }, { "id": "authors:tb1d5-06788", "collection": "authors", "collection_id": "tb1d5-06788", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091630558", "type": "article", "title": "Infrared photometry of the semistellar nucleus of M31", "author": [ { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Sellgren", "given_name": "K.", "clpid": "Sellgren-K" }, { "family_name": "Mould", "given_name": "J.", "orcid": "0000-0003-3820-1740", "clpid": "Mould-J-R" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" } ], "abstract": "New broad-band infrared JHK data and narrow-band CO and H_2O indices for the semistellar nucleus of M31 are presented. The data were obtained specifically to test a prediction of a recent synthesis model by Faber and French in which the ratio of dwarf-to-giant light increases strongly in going from the bulge to the nucleus of M31. The new infrared data do not support such a model. Some alternative explanations for the behavior of the various indices are given, but the apparent conflict between the Faber-French interpretation of the strength of the Na i \u03bb8190 feature and our data is not satisfactorily resolved.", "doi": "10.1086/158290", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1980-09-15", "volume": "240", "pages": "779-784" }, { "id": "authors:87b02-6ws85", "collection": "authors", "collection_id": "87b02-6ws85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091630459", "type": "article", "title": "Luminosities and temperatures of the reddest stars in three LMC clusters", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Infrared observations in the 1.2-2.2 \u00b5m region are presented for 12 of the reddest stars in the Large Magellanic Cloud (LMC) clusters NGC 1783,1846, and 1978. Seven of the stars, which are carbon stars, are photometrically indistinguishable from carbon stars in the general field of the LMC. Bolometric magnitudes and temperatures are derived from the infrared data. The average bolometric magnitude of the carbon stars is \u20144.9, which is about two magnitudes fainter than previously published values, but still high enough to require that these stars are asymptotic giant branch stars. The most luminous M-type stars in these clusters are warmer and perhaps more luminous than the giant branches of metal-rich Galactic globular clusters, in agreement with Hodge's results based on UBV photometry. The location of the M-type stars may present some problems for recent giant branch model calculations.", "doi": "10.1086/158133", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1980-07-15", "volume": "239", "pages": "495-501" }, { "id": "authors:mmr1c-txy32", "collection": "authors", "collection_id": "mmr1c-txy32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-091630056", "type": "article", "title": "PAL 12 - A metal-rich globular cluster in the outer halo", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Zinn", "given_name": "R.", "clpid": "Zinn-R" } ], "abstract": "New optical and infrared observations ofseveral stars in the distant globular cluster Pal 12 show that they have CO strengths and heavy element abundances only slightly less than in M71, one of the more metal-rich globular clusters. Pal 12 thus has a metal abundance near the high end of the range over which globular clusters exist and lies in the outer galactic halo. Its red horizontal branch is not anomalous in view of the abundance we have found.", "doi": "10.1086/158090", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1980-07-01", "volume": "239", "pages": "74-77" }, { "id": "authors:79dye-tze68", "collection": "authors", "collection_id": "79dye-tze68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190531-075354937", "type": "article", "title": "FG Sagittae - 1975 to 1978", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Phillips", "given_name": "A. C.", "clpid": "Phillips-A-C" } ], "abstract": "The spectrum of the extremely peculiar variable star, FG Sagittae, has been followed with high dispersion over the interval from 1975 to 1978, thus continuing the work of Herbig and Boyarchuk and of Langer, Kraft, and Anderson. \n\nA new technique for crude abundance determinations is presented. Using the spectrum ratio method, we find that the steady increase in the s-process element abundances, which began in approximately 1964, has ceased. A cooling of only 500 K is permitted over the 3 years of our observations, at least on the specific dates we observed the star. The agreement between convective time scales derived from a simple application of the mixing length theory and the observed time scale for the s-process episode implies that this event occurred as a result of a convective zone penetrating for a short time into a region where s-process nucleosynthesis had already occurred.", "doi": "10.1086/157848", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1980-04-01", "volume": "237", "pages": "99-104" }, { "id": "authors:zkrw1-dhq74", "collection": "authors", "collection_id": "zkrw1-dhq74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161905266", "type": "article", "title": "The spread in CO absorption and effective temperature among the giants in omega Centauri", "author": [ { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Aaronson", "given_name": "M.", "clpid": "Aaronson-M" }, { "family_name": "Matthews", "given_name": "K.", "clpid": "Matthews-Keith-Astronomy" } ], "abstract": "Infrared photometric observations of 82 stars on the upper giant branch of \u03c9 Centauri are presented. The data show that \u03c9 Cen differs markedly from other globular clusters studied in the infrared in two respects. First, at a given V - K color, there is a wide spread in CO absorption (\u2273 0.1 mag) in the 3 mag interval below the red giant tip; this range is approximately 5 times that found for other clusters. Second, at a given luminosity, V \u2014 K has a spread of up to 1 mag; this range is also much larger than that found for other clusters. The latter result leads us to conclude, in agreement with recent findings by other authors, that there are star-to-star variations in heavy-metal abundance within \u03c9 Cen of a factor of 30 or more. \n\nComparison of the spread in CO absorption with that in V \u2014 K reveals two sequences of stars, one which has \"enhanced\" CO absorption and one which has \"normal\" CO absorption when compared to the run of CO with V \u2014 K among stars in other globular clusters. The proportion of stars having \"enhanced\" CO exceeds 50%. Many of the strong CN stars in the cluster also have \"enhanced\" CO. Explanations for the origin of these sequences which involve primordial abundance variations as well as mixing phenomena are discussed briefly. Implications for the identification of the \"second parameter\" as the CNO abundance are also discussed. Effective temperatures and bolometric luminosities are given for the stars.", "doi": "10.1086/157648", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1980-01-15", "volume": "235", "pages": "452-469" }, { "id": "authors:0kpbr-6cq67", "collection": "authors", "collection_id": "0kpbr-6cq67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161904028", "type": "article", "title": "Abundances in globular cluster red giants. II - M92 and M15", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "A detailed abundance analysis is performed for four stars in M92 and two stars in M15 by using LTE line-blanketed model atmospheres. The deduced result of [Fe/H] with respect to the Sun is \u20142.35 for M92 and \u20142.20 for Ml5. There are no obvious changes in the pattern of abundance as a function of atomic number except for a general lowering by a constant factor when M92 and M13 are compared. The dispersion in the Fe abundance of the M92 stars is very small. Implications for the mass and number of previous generations of stars and for mixing in the protoglobular cluster are discussed.", "doi": "10.1086/157241", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1979-08-01", "volume": "231", "pages": "751-761" }, { "id": "authors:m1my8-5yg37", "collection": "authors", "collection_id": "m1my8-5yg37", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903942", "type": "article", "title": "Observations and interpretations of radial gradients of absorption features in galaxies", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Observations are presented of equivalent widths for strong spectral features with \u03bb > 5000 \u00c5 in the nuclei of five galaxies (M31, M32, M81, NGC 4472, and NGC 3115) as well as the radial gradients of line strength within these galaxies. A theoretical model for predicting the strengths of features in the integrated light of galaxies is also presented. It is concluded, on the basis of this limited sample of galaxies, that the changes in spectral features between galactic nuclei and within galaxies arise from a single causal factor, which is the overall metallicity of the galaxy. The range in nuclear abundance spanned by the five galaxies is a factor of 4. There is no evidence for nonsolar ratios among the elements with lines that have been studied, namely, Ca, Na, Mg, and Fe; specifically, the approximate constancy of the Fe blends within and between galaxies has a natural explanation. Furthermore, the nuclear metallicity ordering is the same as the ordering of M_v.", "doi": "10.1086/156859", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1979-03-01", "volume": "228", "pages": "405-418" }, { "id": "authors:7mtsw-1kg55", "collection": "authors", "collection_id": "7mtsw-1kg55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903850", "type": "article", "title": "Infrared colors, CO band strengths, and physical parameters for giants in M71", "author": [ { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Broad-band J, H, and K magnitudes and narrow-band CO and H_2O indices for 25 giant and horizontal-branch stars in the strong-lined globular cluster M71 are presented. These data are compared with similar data for M67 and for metal-poor globular clusters. In most photometric indices the M71 stars are intermediate between M67 and the metal-poor globulars, although the M71 giant branch extends to considerably cooler temperatures. Bolometric magnitudes and effective temperatures determined for the M71 stars also place this cluster between the other globulars and M67. A theoretical analysis of the CO indices indicates that M71 is metal deficient by 0.4 ( \u00b1 0.2) dex in the mean with respect to field giants. \n\nThe relationship between the CO indices and CN absorption strengths as determined from DDO photometry is as expected from empirically determined temperature dependences and theoretically determined abundance dependences.", "doi": "10.1086/156758", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1979-01-15", "volume": "227", "pages": "499-509" }, { "id": "authors:px66b-3jr69", "collection": "authors", "collection_id": "px66b-3jr69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903769", "type": "article", "title": "Calibration of metallicity effects on the integrated colors of globular clusters and early-type galaxies", "author": [ { "family_name": "Aaronson", "given_name": "Marc", "clpid": "Aaronson-M" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Mould", "given_name": "Jeremy", "orcid": "0000-0003-3820-1740", "clpid": "Mould-J-R" }, { "family_name": "Malkan", "given_name": "Matthew", "orcid": "0000-0001-6919-1237", "clpid": "Malkan-M-A" } ], "abstract": "New infrared observations of globular clusters have been obtained which show that both infrared and optical colors are strongly correlated with metallicity and which provide an empirical calibration of abundance effects in composite stellar systems. Models have been constructed, based on the isochrones of Ciardullo and Demarque, with Z-values between 0.0001 and 0.04, and slope of the initial mass function s between 0 and 4. Metal-poor models with s \u2264 2.35 (the Salpeter function) give good agreement with the empirical calibration. Metal-rich models are compared with observations of the central regions of early-type galaxies, and imply that galaxies which have -19 \u2265 M_v \u2265 -23 correspond to a range in metallicity of 0.0 \u2264 [M/H] \u2264 +0.3. Models with s = 2.35 adequately fit the observations; proper accounting of metallicity effects on narrow-band infrared features does not require s < 2, as previously published models have suggested. An upper limit on s of 3.2 is determined.", "doi": "10.1086/156315", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1978-08-01", "volume": "223", "pages": "824-834" }, { "id": "authors:y8zg9-vnd71", "collection": "authors", "collection_id": "y8zg9-vnd71", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903681", "type": "article", "title": "Abundances in globular cluster red giants. I - M3 and M13", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "A detailed abundance analysis of five red giants in M13 and three in M3 has been performed using line-blanketed model atmospheres. Abundances have been determined for over 20 elements in each star. The mean Fe deficiency is \u20141.6 dex for M13 and \u20141.8 dex for M3, while M3 is marginally more metal-rich in Mg and Si than Ml3. Although all elements (with the probable exception of Na) have the same abundance in each of the five M13 stars, considerable scatter exists for Na and Ca and perhaps other elements in the M3 stars. Fe and elements heavier than Fe have the same abundance in each of the three M3 red giants. It appears impossible to explain all the deduced scatter in M3 either by errors in the analysis or by convective mixing. Therefore, the primordial gas in M3 was not chemically homogeneous during the time interval when star formation of the currently observed M3 red giants took place", "doi": "10.1086/156284", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1978-07-15", "volume": "223", "pages": "487-508" }, { "id": "authors:mgf37-ncn15", "collection": "authors", "collection_id": "mgf37-ncn15", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903515", "type": "article", "title": "Infrared photometry, bolometric magnitudes, and effective temperatures for giants in M3, M13, M92, and M67", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" }, { "family_name": "Persson", "given_name": "S. E.", "clpid": "Persson-S-E" } ], "abstract": "Broad-band infrared J-, H-, and K-magnitudes and narrow-band CO and H_2O indices are presented for a selection of giants reaching 3 mag below the red-giant tip in the globular clusters M3, M13, and M92, and in the old open cluster M67. Comparison of these data with a calculated grid of model atmospheres gives the following results: (1) the models satisfactorily predict the broad-band colors; (2) V \u2014 K measurements accurate to \u00b10.1 mag can be used to give effective temperatures to \u00b1 100 K independent of surface gravity or metal abundance for metal-poor stars; (3) there is disagreement with a previous (T_(eff), spectral type)-calibration based on DDO photometry. \n\nEmpirical bolometric magnitudes are derived by integrating the observed energy distributions out to 2.2 /\u00b5m. The derived luminosities and effective temperatures are plotted in a H-R diagram and are compared with a set of evolutionary tracks for metal-poor stars due to Rood. The agreement is good. \n\nThe CO index, which is sensitive primarily to luminosity and effective temperature for Population I giants, becomes sensitive to metal abundance for very metal-poor stars. The relative metal abundance of M3 and M13 derived from CO is reversed from that derived by some other methods. Some possible explanations are considered. \n\nBecause of the importance of Rayleigh scattering in these cluster stars, B \u2014 V depends on surface gravity. Gravities determined from B \u2014 V colors are used to derive crude masses for the stars. These masses (~0.6 M_\u2299) are roughly consistent with estimates of the turnoff mass. \n\nThe CNO abundances are suggested as the second parameter affecting the color-magnitude diagrams of globular clusters", "doi": "10.1086/156132", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1978-05-15", "volume": "222", "pages": "165-180" }, { "id": "authors:qxeh5-ze592", "collection": "authors", "collection_id": "qxeh5-ze592", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903600", "type": "article", "title": "Bowen mechanism in HZ Herculis", "author": [ { "family_name": "Margon", "given_name": "Bruce", "orcid": "0000-0002-7837-3363", "clpid": "Margon-B" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Most X-ray star companions show \u03bb4640 emission due to an uncertain but probably selective emission process. We have obtained a series of high-dispersion (~14 \u00c5 mm^(-1)) blue and ultraviolet spectra of HZ Her, the companion of the X-ray pulsar Her X-l, using the Mayall 4 m telescope. In addition to the N iii \u03bb4634-4641 emission reported by previous observers, the spectra reveal for the first time the presence of O iii \u03bb3444.1 emission. This provides conclusive evidence that the Bowen fluorescence mechanism is active in HZ Her/Her X-l, in agreement with theoretical predictions by McClintock et al. and Hatchett et al., and suggests that this is also the correct explanation for the \u03bb4640 emission in many such X-ray systems. The observed strengths of the emission features are below those reported in previous lower-dispersion investigations, in some cases very substantially so. The velocities provide no clear resolution of the question of which of the two stars, HZ Her or Her X-l, is associated with the emitting region.", "doi": "10.1086/182686", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1978-05-15", "volume": "222", "pages": "L33-L36" }, { "id": "authors:0ss3r-nek32", "collection": "authors", "collection_id": "0ss3r-nek32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903429", "type": "article", "title": "Near-infrared luminosity-sensitive features in M dwarfs and giants, and in M31 and M32", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Observations are presented of prominent near-infrared spectral features in M dwarfs and M giants which elucidate the behavior of these features (8183-8195 \u00c5 doublet of Na i, the Ca ii triplet, 9910 \u00c5 FeH band, and TiO bands) as a function of luminosity and effective temperature. These spectral features have been measured from near-infrared spectra of the nuclei of M31 and M32. A luminosity function similar to that of the solar neighborhood is supported by our observations. Our measurements indicate an enhancement of metallicity in the nucleus of M31 as compared with that of M32.", "doi": "10.1086/156081", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1978-05-01", "volume": "221", "pages": "788-796" }, { "id": "authors:7mwvj-r4x76", "collection": "authors", "collection_id": "7mwvj-r4x76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903335", "type": "article", "title": "High-velocity gas in the Monoceros loop", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "The interstellar Na i lines arising from high-velocity gas in the Monoceros loop supernova remnant have been observed. When combined with previously published interstellar Ca measurements, the interstellar lines in the high-velocity component of HD 47359 show an abnormally low ratio Na i/Ca ii.", "doi": "10.1086/130193", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1977-10", "series_number": "531", "volume": "89", "issue": "531", "pages": "626" }, { "id": "authors:n57sc-rej03", "collection": "authors", "collection_id": "n57sc-rej03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903214", "type": "article", "title": "Confirmation of the presence of iron hydride in sunspots and cool stars", "author": [ { "family_name": "Wing", "given_name": "Robert F.", "clpid": "Wing-Robert-F" }, { "family_name": "Cohen", "given_name": "Judith", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Brault", "given_name": "James W.", "clpid": "Brault-J-W" } ], "abstract": "A high-resolution sunspot spectrum clearly shows the presence of the 9896 \u00c5 and 8691 \u00c5 bands of iron hydride (FeH). At least 332 lines of the two bands, accounting for 80% of the lines registered in the laboratory, can be identified with certainty in the spot spectrum; most of these are unblended. Our estimate that the 9896 \u00c5 band is 2.0 \u00b1 0.2 times stronger than the 8691 \u00c5 band supports the idea, suggested earlier by laboratory deuteride experiments, that the 9896 \u00c5 band is the (0, 0) transition. No evidence for FeH is found in the spectrum of the solar disk. \n\nImage-tube spectrograms of M dwarfs and S stars have been taken in the near-infrared at 86 \u00c5 mm^(-1) to examine the feature which Nordh, Lindgren, and Wing have proposed is due to the 9896 \u00c5 band of FeH. At this dispersion enough band structure is evident to confirm the identification in both kinds of stars.", "doi": "10.1086/155507", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1977-09-01", "volume": "216", "pages": "659-664" }, { "id": "authors:3edew-azf67", "collection": "authors", "collection_id": "3edew-azf67", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903134", "type": "article", "title": "The interstellar medium near stars with peculiar interstellar polarizations", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "The properties of the interstellar medium along the line of sight to the small number of stars whose wavelength of maximum interstellar polarization is greater than or equal to 6500 \u00c5 are studied. The optical interstellar line measurements reported here confirm the hypothesis that the long \u03bb_(max) phenomenon occurs in regions where the mean grain size is abnormally large, and that this takes place only in the densest parts of the interstellar medium. The grains grow by accretion from the gas, not by coalescence of previously existing grains. Furthermore, the material accreted in the dense clouds (i.e., the mantle) must have a different chemical composition from the grain core; it must consist of substances composed largely of hydrogen", "doi": "10.1086/155232", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1977-05-15", "volume": "214", "pages": "86-91" }, { "id": "authors:f7j0m-zgq87", "collection": "authors", "collection_id": "f7j0m-zgq87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161903043", "type": "article", "title": "Photography at 9400 \u00c5 of infrared and molecular line sources", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Frogel", "given_name": "Jay A.", "clpid": "Frogel-J-A" } ], "abstract": "Photographs with an S-1 image tube at an effective wavelength of 9400 \u00c5 have been obtained for five northern infrared sources. These photographs show objects which do not appear on the Palomar Sky Survey red plates, and which in some cases agree well in position with infrared components of OMC-2, Mon R2, Sh 269, NGC 7538, and OH 0739 -14. The case of OH 0739 -14 is particularly striking. We have found a bright, barlike nebulosity which agrees in position with known infrared and molecular sources. At one end of this bar is a very red stellar object.", "doi": "10.1086/154916", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1977-01-01", "volume": "211", "pages": "178-180" }, { "id": "authors:z6wcd-21m22", "collection": "authors", "collection_id": "z6wcd-21m22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161902938", "type": "article", "title": "A coud\u00e9 camera for image-tube work", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Simmons", "given_name": "J. E.", "clpid": "Simmons-J-E" }, { "family_name": "Maney", "given_name": "S.", "clpid": "Maney-S" } ], "abstract": "A new camera designed specifically for image tubes and modern detectors has been installed at the coud\u00e9 focus of the 2.1-m telescope at Kitt Peak National Observatory. The optical and mechanical design as well as the performance of the camera are discussed.", "doi": "10.1086/130055", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1976-12", "series_number": "526", "volume": "88", "issue": "526", "pages": "966-968" }, { "id": "authors:bf5ek-1kq53", "collection": "authors", "collection_id": "bf5ek-1kq53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161902761", "type": "article", "title": "H\u03b1 emission from the disks of spiral galaxies", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Observations of the amount of Ha emission from the disks of 53 galaxies have been made using\nlarge entrance apertures so that the maximum possible fraction of the total area of the galaxy is\nincluded. These observations reveal a relationship between B - V color and Ha emission; for a\ngiven morphological type the bluer galaxies have more emission at Ha. The effect of the strong\nemission lines on the colors is not sufficient to produce this trend. Furthermore, the Ha emission\ncomes from discrete H II regions ionized by starlight which are limited in the crudest approximation\nby the number of hot stars rather than the availability of gas. From the range in Ha emission,\nwe obtain the ratio of hot stars to cooler stars corresponding to the observed range in B - V\ncolor. We then compare this with a theoretical model by Searle, Sargent, and Bagnuolo which predicts B - V color as a function of the stellar luminosity function in the galaxy. The two separate methods of determining the change in ratio of hot-to-cool stars agree well. We thus give further observational support to the models of Searle, Sargent, and Bagnuolo.", "doi": "10.1086/154115", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1976-02-01", "volume": "203", "pages": "587-592" }, { "id": "authors:at6mp-7ne85", "collection": "authors", "collection_id": "at6mp-7ne85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161902857", "type": "article", "title": "Mass loss in globular cluster red giants", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Echelle spectra of the brightest globular-cluster red giants, taken with the 4 m telescope at Kitt Peak National Observatory, reveal the presence of emission features at H\u03b1. These are interpreted as evidence for a circumstellar envelope, which is produced by mass loss. The gas is being lost at a velocity such that it is possible that the gas is escaping from the globular cluster. An estimate of the rate of mass loss (2 X 10^(-9) M_\u2299 yr^(-1)) is obtained, which agrees well with that expected from revolutionary tracks for the difference in mass between red-giant stars and horizontal-branch stars in globular clusters.", "doi": "10.1086/182035", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1976-02-01", "volume": "203", "pages": "L127-L129" }, { "id": "authors:cjeje-n0y04", "collection": "authors", "collection_id": "cjeje-n0y04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161904766", "type": "book_section", "title": "Diffuse Interstellar Band Formation in Dense Clouds", "book_title": "Solid State Astrophysics", "author": [ { "family_name": "Snow", "given_name": "Theodore P., Jr.", "clpid": "Snow-T-P-Jr" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "contributor": [ { "family_name": "Wickramasinghe", "given_name": "N. C.", "clpid": "Wickramasinghe-N-C" }, { "family_name": "Morgan", "given_name": "D. J.", "clpid": "Morgan-D-J" } ], "abstract": "Measurements of the strengths of the diffuse interstellar bands at 4430, 5780 and 5797 \u00c5 show that the bands tend to be weak with respect to extinction in dense interstellar clouds. Data on 10 stars in the Q Ophiuchi cloud complex show further that the diffuse band-producing efficiency of the grains decreases systematically with increasing grain size. It is concluded that the diffuse bands are not formed in the mantles which accrete on the grains in interstellar clouds, but that they could be produced in the cores of grains or in some molecular species.", "doi": "10.1007/978-94-010-1884-5_5", "isbn": "9789401018869", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "1976", "pages": "33-38" }, { "id": "authors:2whr9-seb75", "collection": "authors", "collection_id": "2whr9-seb75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161902595", "type": "article", "title": "The Interstellar Lines of the Feige Stars", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Meloy", "given_name": "D. A.", "clpid": "Meloy-D-A" } ], "abstract": "New measurements of the equivalent widths and radial velocities of the interstellar lines of Ca ii and Na i in the spectra of Feige stars are presented. The upper limits to the Na i interstellar line imply that the gas in the halo has a much larger value of the ratio of the column density of Ca ii to that of Na i than does the plane, and that this ratio is larger than the intermediate value obtained previously from a group of brighter halo stars. From this we deduce that there is gas up to at least 1 kpc above the plane, and that this gas has much more Ca ii relative to Na i than does the plane. The interstellar equivalent width corresponding to looking out of the Galaxy from the plane at b^(II) = 90\u00b0 is about 300 m\u00c5 for the stronger of the Ca n lines. The velocity measurements imply that this gas is moving slowly toward the plane in a time scale such that replenishment of the halo gas is necessary.", "doi": "10.1086/153631", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1975-06-15", "volume": "198", "pages": "545-549" }, { "id": "authors:a2fgn-jfa78", "collection": "authors", "collection_id": "a2fgn-jfa78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161902503", "type": "article", "title": "Optical interstellar lines in southern supergiants", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Photoelectric photometry of 35 southern supergiants reveals a good correlation of the central residual intensity of the diffuse interstellar line at 4430 \u00c5 with color excess. From spectra of the brighter southern supergiants, I have derived column densities of Na i and Ca ii, and, in a few cases, of CH and CH^+. These results are averaged and compared with previous studies of the interstellar medium at high galactic latitudes and in the denser regions of the plane. The basic peculiarities of the interstellar lines in these two regions, as discussed in Papers I and II, are more sharply delineated by this comparison. Models for the gas in the halo are derived, and I obtained the mass of gas in the halo (from 1 x 10^7 to 6 x 10^7 M_\u2299) and a maximum value of the metal depletion of the halo gas relative to the disk gas (from 300 to 90, depending on whether grains exist in the halo). This maximum value implies that the gas in the halo has been significantly contaminated by material which has undergone nuclear processing.", "doi": "10.1086/153491", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1975-04-01", "volume": "197", "pages": "117-122" }, { "id": "authors:647cb-0x155", "collection": "authors", "collection_id": "647cb-0x155", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161902392", "type": "article", "title": "Diffuse interstellar band formation in dense clouds", "author": [ { "family_name": "Snow", "given_name": "Theodore P., Jr.", "clpid": "Snow-T-P-Jr" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Measurements of the strengths of the diffuse interstellar bands at 4430, 5780 and 5797 \u00c5 show that the bands tend to be week with respect to extinction in dense interstellar clouds. Data on 10 stars in the \u03f1 Ophiuchi cloud complex show further that the diffuse band-producing efficiency of the grains decreases systematically with increasing grain size. It is concluded that the diffuse bands are not formed in the mantles which accrete on the grains in interstellar clouds, but that they could be produced in the cores of grains or in some molecular species.", "doi": "10.1007/bf00646745", "issn": "0004-640X", "publisher": "Springer", "publication": "Astrophysics and Space Science", "publication_date": "1975-04", "series_number": "1", "volume": "34", "issue": "1", "pages": "33-38" }, { "id": "authors:yhcjy-jpx23", "collection": "authors", "collection_id": "yhcjy-jpx23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161902094", "type": "article", "title": "Diffuse interstellar band formation in dense clouds", "author": [ { "family_name": "Snow", "given_name": "Theodore P., Jr.", "clpid": "Snow-T-P-Jr" }, { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Data are presented which show that the strengths of the diffuse interstellar bands at 4430, 5780, and 5797 A tend to be deficient with respect to color excess in the lines of sight to stars lying behind dense interstellar clouds. In addition, diffuse-band data for ten stars in the well-studied rho Ophiuchi cloud complex are presented, and systematic variations of band strengths with optical depth are discussed. It is found that the band strength per grain in the line of sight apparently decreases with increasing grain size, taking the ratio of total-to-selective absorption and the wavelength of maximum polarization as indicators of the latter. It is concluded that diffuse-band formation probably takes place most efficiently in the outer regions of interstellar clouds. This may be consistent with a diffuse-band origin in small grains which are coated by mantles in cloud interiors; or in some molecule or molecules which are most abundant in the outer portions of interstellar clouds.", "doi": "10.1086/153247", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1974-12-01", "volume": "194", "pages": "313-322" }, { "id": "authors:zaef6-71688", "collection": "authors", "collection_id": "zaef6-71688", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161902015", "type": "article", "title": "Interstellar lines in stars at high galactic latitudes", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We have measured the velocity and equivalent widths of the optical interstellar lines in a group of southern B stars at high galactic latitudes, as well as additional data for the stars previously discussed by M\u00fcnch and Zirin. The main peculiarities of the interstellar matter far above the plane seem to be an increase in the ratio of the column density of Ca ii to that of Na i and, less certainly, an excess of Ca ii relative to H i. The gas-to-dust ratio indicates that some of the hydrogen at high galactic latitudes may be ionized.", "doi": "10.1086/153219", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1974-11-15", "volume": "194", "pages": "37-40" }, { "id": "authors:1m68x-sst65", "collection": "authors", "collection_id": "1m68x-sst65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161901928", "type": "article", "title": "Optical interstellar lines in dark clouds. II. K i and ultraviolet sodium lines", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "New observations of the K i and ultraviolet Na i interstellar lines are presented for some stars embedded in dense clouds and for a few supergiants. The new observations of weak lines, which are essentially unaffected by the adopted velocity distribution for the interstellar material, support the conclusions previously obtained from the interstellar D-lines of Na i and H- and K-lines of Ca ii The new data, when combined with a discussion of the ionization equilibrium, indicate no or moderate depletions at the edges of clouds, but some depletions in the central regions.", "doi": "10.1086/153068", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1974-09-01", "volume": "192", "pages": "379-382" }, { "id": "authors:ybyhv-r5e25", "collection": "authors", "collection_id": "ybyhv-r5e25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-161901804", "type": "article", "title": "On the velocity structure of the interstellar clouds near rho Ophiuchi", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Wallerstein", "given_name": "George", "orcid": "0000-0003-3416-8728", "clpid": "Wallerstein-G" } ], "abstract": "Accurate radial velocities of the optical interstellar features for some of the B stars embedded in the \u03c1 Oph complex are obtained by averaging results of several photographic high-dispersion spectra. In at least one case, there is a real difference between the radial velocity of the atomic features (Na i and Ca ii) and the molecular ones (CH and CN). We show that it is probable that the CH and CN are concentrated either in a separate cloud (i.e., region of space) from the Ca ii and Na i or in a cloud whose outer parts are expanding rather than in a single cloud which is contracting or rotating.", "doi": "10.1086/152797", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1974-04-15", "volume": "189", "pages": "259-261" }, { "id": "authors:jq2mt-yfr83", "collection": "authors", "collection_id": "jq2mt-yfr83", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832307", "type": "article", "title": "On the Reality of the High Lithium Abundances in Carbon Stars", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Because of recent advances in model atmospheres for cool stars, there may be some doubt as to the validity of previous estimates of the Li abundance in the super-Li stars. Through the behavior of the resonance lines of K i, we show that these analyses are correct, and that the super-Li stars represent a real abundance peculiarity of Li. Key words: super-Li stars - Li abundances", "doi": "10.1086/129553", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1974-02", "series_number": "509", "volume": "86", "issue": "509", "pages": "31-32" }, { "id": "authors:nj8w2-gpn05", "collection": "authors", "collection_id": "nj8w2-gpn05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103834518", "type": "article", "title": "Optical interstellar lines in dark clouds", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Observations of the equivalent widths and radial velocities of the interstellar lines of Ca ii, Na i, CH, and CH^+ are presented for 30 stars. A special effort was made to observe stars behind or within dense clouds with up to 3 mag of absorption. The interstellar lines in the cloud stars are compared with those in a group of highly reddened supergiants whose reddening arises from a large distance, i.e., a long path length through relatively thin material. The atomic interstellar lines of the cloud stars are weak compared to those of supergiants with the same color excess; the molecular lines are of comparable strength in the two groups, except that the ratio n_(CH)/n_(CH^+) is larger in the cloud stars. The ionization equilibrium is discussed, and it is concluded that the deficiency of atomic Ca and Na relative to hydrogen in the clouds is about a factor of 100 larger than in the supergiants.", "doi": "10.1086/152483", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1973-11-15", "volume": "186", "pages": "149-163" }, { "id": "authors:3tz4c-xwa87", "collection": "authors", "collection_id": "3tz4c-xwa87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103834433", "type": "article", "title": "A Search for High-Excitation Redshift Systems in the Absorption Spectra of Five Quasars", "author": [ { "family_name": "Bahcall", "given_name": "J. N.", "clpid": "Bahcall-J-N" }, { "family_name": "Joss", "given_name": "P. C.", "clpid": "Joss-P-C" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "We have searched the absorption spectra of five quasars for the presence of redshift system dominated by the highly ionized doublets C iv, N v, and O vi, which could be the strongest lines produced by absorbing clouds with collisional ionization temperatures between 10^5 \u00b0 and 10^6 \u00b0K. There is at most marginal evidence for one such system apiece in the spectra of PHL 957 and 4C 05.34, which are the two quasars with the largest known emission redshifts. Highly ionized redshift systems of this type are not widespread among the five quasars we investigated; the number of redshifts found in the observed spectra is not significantly larger than the number found in similar random-number spectra. Less than 5 percent of the observed absorption lines are identified in a statistically significant way by redshift systems of this type.", "doi": "10.1086/152303", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1973-08-15", "volume": "184", "pages": "57-63" }, { "id": "authors:b86yf-wdj54", "collection": "authors", "collection_id": "b86yf-wdj54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103834357", "type": "article", "title": "The Absorption Lines in Quasi-Stellar Objects", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "The gas producing the absorption lines seen in the spectra of some high-redshift QSOs can be physically related to the QSO or it can be located by chance on the line of sight to the quasar. If it is physically adjacent to the quasar, it will be photoionized and the observed pattern of absorption lines can be produced. However, an ejection model has great difficulty explaining the sharpness of the observed absorption features compared with the large difference between absorption and emission redshift. A model in which the gas is part of the intergalactic medium or the extreme outer parts of galaxies is discussed. In this case, the gas may be collisionally ionized. To produce the observed ions C iv, N v, and O vi in absorption, the temperature must be about 10^5 \u00b0K. For solar metal abundance, it is then surprising that La is the strongest line in absorption. An attempt to enhance the La absorption by adding a cool region in which hydrogen is predominantly neutral fails as this region is photoionized by radiation from the hot region. Therefore, the metal abundance in the absorbing gas must be less than solar if the gas is not photoionized.", "doi": "10.1086/152076", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1973-05-01", "volume": "181", "pages": "619-625" }, { "id": "authors:q0c2z-w1q97", "collection": "authors", "collection_id": "q0c2z-w1q97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832225", "type": "article", "title": "Technetium in S Sculptoris", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Evidence is given for the presence of technetium in S Sci, a long-period Me variable.", "doi": "10.1086/129431", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1973-04", "series_number": "504", "volume": "85", "issue": "504", "pages": "187" }, { "id": "authors:491t1-fr405", "collection": "authors", "collection_id": "491t1-fr405", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103834273", "type": "article", "title": "Diffuse Nebulae at High Galactic Latitudes", "author": [ { "family_name": "Grasdalen", "given_name": "G.", "clpid": "Grasdalen-G" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "The nature of the diffuse nebulae at high galactic latitudes is discussed. Although these nebulae show H\u03b2 in emission, evidence is presented that they are reflection nebulae illuminated by the integrated light of the Galaxy. Observational evidence for this suggestion is obtained by narrow-band photometry of external spiral galaxies with large entrance apertures. In the integrated spectra of spiral disks, we find that H\u03b1 is in emission.", "doi": "10.1086/181142", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1973-02-15", "volume": "180", "pages": "L11-L13" }, { "id": "authors:ggdh6-m0069", "collection": "authors", "collection_id": "ggdh6-m0069", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103834182", "type": "article", "title": "A spectroscopic study of the molecular constituents of dark clouds", "author": [ { "family_name": "Chaffee", "given_name": "F. H., Jr.", "clpid": "Chaffee-F-H-Jr" }, { "family_name": "Strom", "given_name": "S. E.", "clpid": "Strom-S-E" }, { "family_name": "Lutz", "given_name": "B.", "clpid": "Lutz-B" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "[no abstract]", "doi": "10.1086/129350", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1972-10", "volume": "84", "pages": "639-640" }, { "id": "authors:ydfa7-1js64", "collection": "authors", "collection_id": "ydfa7-1js64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103834085", "type": "article", "title": "Physical Sciences: Multiple Redshifts in QSOs", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Four QSOs (PHL 957, Ton 1530, Parkes 0237\u201323, and 4C 05.34) are now known with complex absorption spectra; these have been interpreted as objects with multiple redshifts. It is disturbing that even with the use of up to 10 redshifts per object, 20% or more of the absorption lines which are definitely present with strength 2 or greater remain unidentified.", "doi": "10.1038/237273a0", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "1972-06-02", "series_number": "5353", "volume": "237", "issue": "5353", "pages": "273" }, { "id": "authors:efqyj-5p797", "collection": "authors", "collection_id": "efqyj-5p797", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103833996", "type": "article", "title": "The Lithium Isotope Ratio in F and G Field Stars", "author": [ { "family_name": "Cohen", "given_name": "Judith Gamora", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "A Fabry-Perot interferometer was used to obtain high-resolution profiles of the resonance line of Li i and \u03bb6717.69 of Ca i in 14 bright F, G, and early K field stars. The observational data were fitted by computed theoretical line profiles to determine the rotational velocity, Li abundance, and Li isotope ratio for each star. The ^6Li/^7Li ratio was 0.1 or less in all the program stars", "doi": "10.1086/151259", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1972-01-01", "volume": "171", "pages": "71-77" }, { "id": "authors:h7c1p-4zp40", "collection": "authors", "collection_id": "h7c1p-4zp40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832137", "type": "article", "title": "Nature of BD + 17\u00b0 4708", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Greenstein", "given_name": "Jesse L.", "clpid": "Greenstein-J-L" } ], "abstract": "Oke, Greenstein, and Gunn (1966) called the GO star BD + 17\u00b0 4708 a field horizontal-branch star. They determined its effective temperature to be 6000\u00b0 K, and its surface gravity as log g = 3.0. In his study of field horizontal-branch stars, Newell (1969) found + 17\u00b0 4708 to be the reddest such star, and it occupied a critical position in his plot of 0_e vs. log g, serving to separate more clearly the groups he calls disk horizontal-branch and halo horizontal-branch stars. It is the purpose ofthis note to indicate that + 17\u00b0 4708 is a G subdwarf, possibly slightly evolved, rather than a field horizontal-branch star.", "doi": "10.1086/129017", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1970-10", "series_number": "489", "volume": "82", "issue": "489", "pages": "1152-1156" }, { "id": "authors:626wm-jan69", "collection": "authors", "collection_id": "626wm-jan69", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103832022", "type": "article", "title": "Continuum of M 31 in the Nuclear Bulge", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Sandage, Becklin, and Neugebauer (1969) have confirmed and extended the color aperture relation for M 31 over the region within T from the nucleus first reported by de Vaucouleurs and Tifft (de Vaucouleurs 1961). In view of the importance of the spectral energy distribution of M31 in determining the K correction, and also the possible variation of stellar content with distance from the nucleus, we have extended these measurements to larger apertures.", "doi": "10.1086/128958", "issn": "0004-6280", "publisher": "Astronomical Society of the Pacific", "publication": "Publications of the Astronomical Society of the Pacific", "publication_date": "1970-06", "series_number": "487", "volume": "82", "issue": "487", "pages": "760-762" }, { "id": "authors:veysz-4xw13", "collection": "authors", "collection_id": "veysz-4xw13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103831934", "type": "article", "title": "Spectrum of a^2 CVn. II", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "The behavior of the continuum of a^2 CVn has been studied. The Balmer discontinuity does not vary but the slope of the Paschen continuum changes over the cycle. The line-blanketing coefficients have been measured at several phases and do not change sufficiently to produce the observed variations of the continuum. The effective temperature (12000\u00b0 K) and surface gravity (log g = 4.0) are determined from the scans and hydrogen-line profiles, and the behavior of equivalent width as a function of phase is discussed. A crude abundance analysis is performed, which shows that the iron peak is enhanced above the solar value and that the rare earths are even more overabundant than was previously thought. The results of the abundance analysis are discussed in terms of a first-order oblique-rotator model, and the implications for the theory of Ap stars are described.", "doi": "10.1086/150325", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1970-02", "volume": "159", "pages": "473-484" }, { "id": "authors:0wy6b-w1s75", "collection": "authors", "collection_id": "0wy6b-w1s75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103831840", "type": "article", "title": "Spectrum of a^2; Canum Venaticorum, 5000-6700 \u00c5", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Deutsch", "given_name": "Armin J.", "clpid": "Deutsch-A-J" }, { "family_name": "Greenstein", "given_name": "Jesse L.", "clpid": "Greenstein-J-L" } ], "abstract": "A complete list is given of all lines observed between 5000 and 6650 \u00c5 in the spectrum of a^2 CVn. Approximately three-quarters of the features have been identified. Lines of Pb ii and P ii are not present. Lines of Gd m and Pr m vary in equivalent width and radial velocity in a manner similar to the singly ionized rare earths. Lines of Cl ii are present and also behave like those of a rare earth.", "doi": "10.1086/149994", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1969-05", "series_number": "2", "volume": "156", "issue": "2", "pages": "629-651" }, { "id": "authors:3a51k-m9b85", "collection": "authors", "collection_id": "3a51k-m9b85", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103831756", "type": "article", "title": "Analysis of F and G Subdwarfs. III. An Abundance Analysis of the Subdwarf \u03bc Cassiopeia", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Equivalent widths of lines with \u03bb > 4600 \u00c5 were measured from a set of 4.5 \u00c5 mm^(-1) Palomar plates and were used in performing a model-atmosphere abundance analysis of the mild subdwarf \u00b5 Cas. Comparison with the Sun was made by computing abundances from individual solar lines using the same set of transition probabilities as was used for the subdwarf. Results of this analysis show that the iron-peak elements appear to be deficient by a factor of 4, while the \u03b1 process in \u00b5 Cas elements may be enhanced with respect to these elements.", "doi": "10.1086/149748", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1968-10", "volume": "154", "pages": "179-184" }, { "id": "authors:mg454-b1x75", "collection": "authors", "collection_id": "mg454-b1x75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103831668", "type": "article", "title": "Analysis of F and G Subdwarfs. II. A Model-Atmosphere Abundance Analysis of the Subdwarfs HD 140283 and HD 19445", "author": [ { "family_name": "Cohen", "given_name": "Judith G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Strom", "given_name": "Stephen E.", "clpid": "Strom-S-E" } ], "abstract": "A grid of model atmospheres has been used to perform an abundance analysis of these two extreme Population II stars. \n\nThe abundances determined from the models confirm the general results of previous investigations, namely that metals are deficient by a factor of about 100 relative to average Population I abundances. A marginal deficiency of s-process material relative to the average deficiency is found; the carbon deficiencies are comparable to those of the other elements and for HD 19445 the \u03b1-process elements are enhanced. From the analysis it also appears that convection plays a significant role in determining the temperature structure of subdwarf atmospheres.", "doi": "10.1086/149462", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1968-02", "volume": "151", "pages": "623-636" }, { "id": "authors:jhwbq-yep62", "collection": "authors", "collection_id": "jhwbq-yep62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103831576", "type": "article", "title": "Limits on the C^(12)/C^(13)Ratio in Metal-Deficient Stars", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Grasdalen", "given_name": "G. L.", "clpid": "Grasdalen-G-L" } ], "abstract": "Lower limits for the ratio C^(12)/C^(13) have been determined for eight metal-deficient stars. These limits are inconsistent with the predictions of nearly all of the universal models considered by Wagoner, Fowler, and Hoyle (1967) unless at least one generation of massive, rapidly evolving stars existed before the formation of any of the program stars.", "doi": "10.1086/180136", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1968-01", "volume": "151", "pages": "L41-L43" }, { "id": "authors:k7x34-05b49", "collection": "authors", "collection_id": "k7x34-05b49", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190610-100620711", "type": "article", "title": "The Carbon Abundance of Population II Stars", "author": [ { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" } ], "abstract": "Curve of growth analyses available to date for Population II stars have indicated that carbon is more deficient relative to the sun than iron. A refined treatment, which takes into account stratification and molecular equilibrium, shows that carbon is not more deficient than iron, assuming a solar oxygen-to-iron ratio.", "issn": "0004-6388", "publisher": "Gordon and Breach", "publication": "Astrophysical Letters", "publication_date": "1968", "volume": "2", "pages": "163-164" }, { "id": "authors:dswyp-8sj65", "collection": "authors", "collection_id": "dswyp-8sj65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190529-103831472", "type": "article", "title": "Analysis of F and G Subdwarfs. I. The Location of Subdwarfs in the Theoretical H-R Diagram", "author": [ { "family_name": "Strom", "given_name": "S. E.", "clpid": "Strom-S-E" }, { "family_name": "Cohen", "given_name": "J. G.", "orcid": "0000-0002-8039-4673", "clpid": "Cohen-J-G" }, { "family_name": "Strom", "given_name": "K. M.", "clpid": "Strom-K-M" } ], "abstract": "Spectrum scans and model stellar atmospheres have been used to locate in the (L/L_\u2299, T_(eff)) plane F and G subdwarfs having known parallax A comparison is made between their position on the H-R diagram and the evolutionary tracks for Population II models of low- and high-helium content recently computed by Faulkner and Iben. The lower helium-content models are found to give somewhat more plausible ages than the high-helium models. Nevertheless, for both the low- and high-helium-content models, we find several subdwarfs with ages apparently greater than 10 X 10^9 years.", "doi": "10.1086/149093", "issn": "0004-637X", "publisher": "American Astronomical Society", "publication": "Astrophysical Journal", "publication_date": "1967-03", "volume": "147", "pages": "1038-1049" } ]