[ { "id": "authors:tdmdk-zg231", "collection": "authors", "collection_id": "tdmdk-zg231", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180330-101945072", "type": "book_section", "title": "Observational Details: Radio", "book_title": "Relativistic Jets from Active Galactic Nuclei", "author": [ { "family_name": "Bridle", "given_name": "A. H.", "clpid": "Bridle-A-H" }, { "family_name": "Cohen", "given_name": "M. H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" } ], "contributor": [ { "family_name": "Krawczynski", "given_name": "Henric", "clpid": "Krawczynski-H-S" } ], "abstract": "In this chapter we discuss the observations of radio jets. After some introductory remarks, mainly describing the classic Fanaroff\u2013Riley separation of double radio sources, we separate the topic into small-scale (parsec) and large-scale (kiloparsec) jets. These two types of objects have been studied with different telescopes and the two subfields have developed largely independently of each other. Very Long Baseline Interferometry (VLBI) with angular resolution of 1 milliarcsecond (mas) and better is used at parsec (pc) scales, and the Very Large Array (VLA) and similar instruments are used for larger scales. VLBI is sensitive only to high surface-brightness features (\u2273 10^5 K) and so typically studies only the core region of a source; whereas the VLA can image the faint outer plumes of a radio galaxy but its core region is subsumed into an unresolved bright spot. This instrumental distinction,\nhowever is not definitive, as some observations at certain frequencies cover the intermediate range, e.g., MERLIN and its connections to the European VLBI Network cover a wide range of scales. See Figure 1.1 for a montage of VLBI and VLA images that span the pc\u2013kpc range.", "doi": "10.1002/9783527641741.ch5", "isbn": "9783527410378", "publisher": "Wiley", "place_of_publication": "Weinheim", "publication_date": "2012-02-06", "pages": "115-152" }, { "id": "authors:hhkgd-2yx93", "collection": "authors", "collection_id": "hhkgd-2yx93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190826-124741053", "type": "book_section", "title": "Dark Matter and the Owens Valley Radio Observatory", "book_title": "The New Astronomy: Opening the Electromagnetic Window and Expanding Our View of Planet Earth", "author": [ { "family_name": "Cohen", "given_name": "Marshall", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" } ], "contributor": [ { "family_name": "Orchiston", "given_name": "Wayne", "clpid": "Orchiston-W" } ], "abstract": "Neutral hydrogen gas in a spiral galaxy generally extends far beyond the visible stars, and radio observations that can detect this hydrogen were used to study galactic rotation to great distances. Around 1970, radio astronomers showed that the rotation curves were flatter than Keplerian beyond the optically visible galaxy, and hence that they had to contain a large amount of invisible, or dark, matter. The interferometer at the Owens Valley Radio Observatory was able to study this in greater detail than was possible with the filled-aperture telescopes that existed then, and made the first curves that were unambiguously flat. Within a half-dozen years, however, the field became dominated by more powerful instruments. With these the rotation curves were extended and many more galaxies were measured, and by the late 1970s astronomers generally had become convinced of the need for dark matter.", "doi": "10.1007/1-4020-3724-4_9", "isbn": "9781402037238", "publisher": "Springer", "place_of_publication": "Dordrecht", "publication_date": "2005", "pages": "169-182" }, { "id": "authors:ds4f3-9be68", "collection": "authors", "collection_id": "ds4f3-9be68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20110316-110010838", "type": "book_section", "title": "Relativistic phenomena in active galactic nuclei", "book_title": "Radio astronomy from Karl Jansky to microjansky", "author": [ { "family_name": "Cohen", "given_name": "M. H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" }, { "family_name": "Lister", "given_name": "M. L.", "orcid": "0000-0003-1315-3412", "clpid": "Lister-M-L" }, { "family_name": "Vermeulen", "given_name": "R. C.", "clpid": "Vermeulen-R-C" } ], "contributor": [ { "family_name": "Gurvits", "given_name": "Leonid I.", "clpid": "Gurvits-L-I" }, { "family_name": "Frey", "given_name": "S\u00e1ndor", "clpid": "Frey-S" }, { "family_name": "Rawlings", "given_name": "Steve", "clpid": "Rawlings-S" } ], "abstract": "The idea that the radio jets in AGN contain material in relativistic motion is supported by many lines of observational evidence, including morphology, brightness temperature estimated with interferometers and with intrinsic variations, interstellar scintillations, X-rays, and superluminal motion. These are largely independent, and taken together make an irrefutable case for relativistic motion.", "doi": "10.1051/eas:2005148", "isbn": "2-86883-735-2", "publisher": "EDP Sciences", "place_of_publication": "Les Ulis", "publication_date": "2005", "pages": "93-107" }, { "id": "authors:ah7h5-ktk07", "collection": "authors", "collection_id": "ah7h5-ktk07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191127-100958634", "type": "book_section", "title": "Formation and Evolution of Planetary Systems: SIRTF Legacy Science in the VLT Era", "book_title": "The Origin of Stars and Planets: The VLT View", "author": [ { "family_name": "Meyer", "given_name": "M. R.", "orcid": "0000-0003-1227-3084", "clpid": "Meyer-M-R" }, { "family_name": "Backman", "given_name": "D.", "clpid": "Backman-D-E" }, { "family_name": "Beckwith", "given_name": "S. V. W.", "clpid": "Beckwith-S-V-W" }, { "family_name": "Brooke", "given_name": "T. Y.", "clpid": "Brooke-T-Y" }, { "family_name": "Carpenter", "given_name": "J. M.", "orcid": "0000-0003-2251-0602", "clpid": "Carpenter-J-M" }, { "family_name": "Cohen", "given_name": "M.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" }, { "family_name": "Gorti", "given_name": "U.", "clpid": "Gorti-U" }, { "family_name": "Henning", "given_name": "T.", "clpid": "Henning-Thomas" }, { "family_name": "Hillenbrand", "given_name": "L. A.", "clpid": "Hillenbrand-L-A" }, { "family_name": "Hines", "given_name": "D.", "orcid": "0000-0003-4653-6161", "clpid": "Hines-D-C" }, { "family_name": "Hollenbach", "given_name": "D.", "clpid": "Hollenbach-D-J" }, { "family_name": "Lunine", "given_name": "J.", "orcid": "0000-0003-2279-4131", "clpid": "Lunine-Jonathan-Irving" }, { "family_name": "Malhotra", "given_name": "R.", "orcid": "0000-0002-1226-3305", "clpid": "Malhotra-Renu" }, { "family_name": "Mamajek", "given_name": "E.", "orcid": "0000-0003-2008-1488", "clpid": "Mamajek-E-E" }, { "family_name": "Morris", "given_name": "P.", "orcid": "0000-0002-5186-4381", "clpid": "Morris-P-W" }, { "family_name": "Najita", "given_name": "J.", "clpid": "Najita-Joan-R" }, { "family_name": "Padgett", "given_name": "D. L.", "orcid": "0000-0001-5334-5107", "clpid": "Padgett-D-L" }, { "family_name": "Soderblom", "given_name": "D.", "orcid": "0000-0002-0322-8161", "clpid": "Soderblom-D-R" }, { "family_name": "Stauffer", "given_name": "J.", "orcid": "0000-0003-3595-7382", "clpid": "Stauffer-J-R" }, { "family_name": "Strom", "given_name": "S. E.", "clpid": "Strom-S-E" }, { "family_name": "Watson", "given_name": "D.", "clpid": "Watson-D" }, { "family_name": "Weidenschilling", "given_name": "S.", "clpid": "Weidenschilling-S" }, { "family_name": "Young", "given_name": "E.", "clpid": "Young-E-T" } ], "contributor": [ { "family_name": "Alves", "given_name": "Jo\u00e3o F.", "clpid": "Alves-J-F" }, { "family_name": "McCaughrean", "given_name": "Mark J.", "clpid": "McCaughrean-M-J" } ], "abstract": "We will utilize the sensitivity of SIRTF through the Legacy Science Program to carry out spectrophotometric observations of solar-type stars aimed at (1) defining the timescales over which terrestrial and gas giant planets are built, from measurements diagnostic of dust/gas masses and radial distributions; and (2) establishing the diversity of planetary architectures and the frequency of planetesimal collisions as a function of time through observations of circumstellar debris disks. Together, these observations will provide an astronomical context for understanding whether our solar system - and its habitable planet - is a common or a rare circumstance.\n\nAchieving our science goals requires measuring precise spectral energy distributions for a statistically robust sample capable of revealing evolutionary trends and the diversity of system outcomes. Our targets have been selected from two carefully assembled databases of solar-like stars: (1) a sample located within 50 pc of the Sun spanning an age range from 100-3000 Myr for which a rich set of ancillary measurements (e.g. metallicity, stellar activity, kinematics) are available; and (2) a selection located between 15 and 180 pc and spanning ages from 3 to 100 Myr. For stars at these distances SIRTF is capable of detecting stellar photospheres with SNR >30 at \u03bb\u226424\u03bc m for our entire sample, as well as achieving SNR >5 at the photospheric limit for over 50% of our sample at \u03bb=70\u03bc m. Thus we will provide a complete census of stars with excess emission down to the level produced by the dust in our present-day solar system.\n\nSIRTF observations obtained as part of this program will provide a rich Legacy for follow-up observations utilizing a variety of facilities including the VLT. More information concerning our program can be found at http://gould.as.arizona.edu/feps.", "doi": "10.1007/10856518_60", "isbn": "978-3-540-43541-9", "publisher": "Springer", "place_of_publication": "Berlin", "publication_date": "2003-10-15", "pages": "463-472" }, { "id": "authors:paxmr-1tc93", "collection": "authors", "collection_id": "paxmr-1tc93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181213-143635374", "type": "book_section", "title": "LRIS imaging spectropolarimeter at the W. M. Keck Observatory", "book_title": "Polarimetry in Astronomy", "author": [ { "family_name": "Goodrich", "given_name": "Robert W.", "clpid": "Goodrich-R-W" }, { "family_name": "Cohen", "given_name": "Marshall H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" } ], "contributor": [ { "family_name": "Fineschi", "given_name": "Silvano", "clpid": "Fineschi-S" } ], "abstract": "An optical-wavelength polarimetry module has been in use for the past ten years at the W.M. Keck Observatory. The module is used in conjunction with the LRIS imaging spectrograph. It provides either imaging polarimetry or spectropolarimetry across the full wavelength range of the instrument (320-1100 nm). The design, performance, and limitations of the polarimetry module are described, along with a sampling of science results.", "doi": "10.1117/12.458652", "isbn": "9780819446220", "publisher": "Society of Photo-optical Instrumentation Engineers (SPIE)", "place_of_publication": "Bellingham, WA", "publication_date": "2003-02-14", "pages": "146-155" }, { "id": "authors:k533w-e8s50", "collection": "authors", "collection_id": "k533w-e8s50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201027-183158089", "type": "book_section", "title": "Optical Polarization of 3C 265", "book_title": "Extragalactic Radio Sources", "author": [ { "family_name": "Cohen", "given_name": "M. H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" }, { "family_name": "Tran", "given_name": "H. D.", "clpid": "Tran-Hien-D" }, { "family_name": "Ogle", "given_name": "P. M.", "orcid": "0000-0002-3471-981X", "clpid": "Ogle-P-M" }, { "family_name": "Goodrich", "given_name": "R. W.", "clpid": "Goodrich-R-W" } ], "contributor": [ { "family_name": "Ekers", "given_name": "R.", "clpid": "Ekers-R" }, { "family_name": "Fanti", "given_name": "C", "clpid": "Fanti-C" }, { "family_name": "Padrielli", "given_name": "L", "clpid": "Padrielli-L" } ], "abstract": "3C 265 is a high-redshift (z=0.811) radio galaxy showing extended emission line regions (EELR) to 50 kpc from the nucleus (McCarthy et al 1995). However, it does not show the alignment effect (McCarthy 1993) that is common in distant galaxies: the EELR is not extended along the radio axis.", "doi": "10.1007/978-94-009-0295-4_78", "isbn": "9780792341222", "publisher": "Springer Netherlands", "place_of_publication": "Dordrecht", "publication_date": "1996", "pages": "223-226" }, { "id": "authors:8w6h1-vxf65", "collection": "authors", "collection_id": "8w6h1-vxf65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201008-131242874", "type": "book_section", "title": "Statistics of superluminal sources", "book_title": "BL Lac Objects", "author": [ { "family_name": "Cohen", "given_name": "Marshall H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" } ], "contributor": [ { "family_name": "Maraschi", "given_name": "L.", "clpid": "Maraschi-L" }, { "family_name": "Maccacaro", "given_name": "T.", "clpid": "Maccacaro-T" }, { "family_name": "Ulrich", "given_name": "M.-H.", "clpid": "Ulrich-M-H" } ], "abstract": "The probability density that a randomly selected beamed source lies at angle \u03b8 to the line of sight is shown in Fig. 3. For reasonable values of the Lorentz factor, the Doppler boost exponent and the N(S) exponent, p(\u03b8) peaks at a few degrees, well inside the angle for maximum apparent transverse velocity. Theoretical distributions of the apparent transverse velocity are sharply peaked near the maximum possible value, but the observed distribution is peaked at low velocities. Some of the difference is due to the inhomogeneous nature of the sample. BL Lacs have a lower average velocity than quasars. From a purely statistical point of view this might be due to their being the low-\u03b8 tail of the quasar distribution; this also would help to explain the rapid intensity variations and high continuum/line ratios. However this explanation is unlikely, because the redshift distributions are so different.", "doi": "10.1007/bfb0031139", "isbn": "978-3-540-51389-6", "publisher": "Springer-Verlag", "place_of_publication": "Berlin/Heidelberg", "publication_date": "1989", "pages": "13-21" }, { "id": "authors:841ja-rjc65", "collection": "authors", "collection_id": "841ja-rjc65", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181115-154916201", "type": "book_section", "title": "Expanding Quasars and the Expansion of the Universe", "book_title": "The Impact of VLBI on Astrophysics and Geophysics", "author": [ { "family_name": "Cohen", "given_name": "M. H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" }, { "family_name": "Barthel", "given_name": "P. D.", "orcid": "0000-0002-0106-5776", "clpid": "Barthel-P-D" }, { "family_name": "Pearson", "given_name": "T. J.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" }, { "family_name": "Zensus", "given_name": "J. A.", "clpid": "Zensus-J-A" } ], "contributor": [ { "family_name": "Reid", "given_name": "M. J.", "clpid": "Reid-M-J" }, { "family_name": "Moran", "given_name": "J. M.", "clpid": "Moran-J-M" } ], "abstract": "The \u03bc\u2013z diagram (Figure 1) plots the observed internal proper motion \u03bc versus redshift z for 32 extragalactic radio sources associated with active galactic nuclei. The observed points fall below an upper bound which decreases with redshift; there is a statistically significant anticorrelation between redshift and internal proper motion.", "doi": "10.1017/S0074180900133820", "isbn": "9789027727046", "publisher": "Kluwer", "place_of_publication": "Dordrecht", "publication_date": "1988", "pages": "23-24" }, { "id": "authors:4tarx-c7211", "collection": "authors", "collection_id": "4tarx-c7211", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181211-155619617", "type": "book_section", "title": "VLA Polarimetry of VLBI Core\u2013Jet Sources", "book_title": "The Impact of VLBI on Astrophysics and Geophysics", "author": [ { "family_name": "Wrobel", "given_name": "J. M.", "orcid": "0000-0001-9720-7398", "clpid": "Wrobel-J-M" }, { "family_name": "Pearson", "given_name": "T. J.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" }, { "family_name": "Cohen", "given_name": "M. H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" }, { "family_name": "Readhead", "given_name": "A. C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" } ], "contributor": [ { "family_name": "Reid", "given_name": "Mark Jonathan", "clpid": "Reid-M-J" }, { "family_name": "Moran", "given_name": "J. M.", "clpid": "Moran-J-M" } ], "abstract": "Radio imaging of VLBI core-jet sources can be used to examine the case for continuity of jet-like features between parsec and circumgalactic scales. Futhermore, polarimetry of such sources allows investigation of the dominant magnetic field topologies as a function of linear offset from the central engine. Examination of these continuity and field topology issues is essential for an understanding of how energy is channeled from the nuclear regions to the circumgalactic environment.", "doi": "10.1017/S0074180900134394", "isbn": "9789027727046", "publisher": "Kluwer", "place_of_publication": "Dordrecht", "publication_date": "1988", "pages": "165-166" }, { "id": "authors:07e1p-gmt46", "collection": "authors", "collection_id": "07e1p-gmt46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200929-163431392", "type": "book_section", "title": "Radio sources: Small scale structure", "book_title": "Active Galactic Nuclei", "author": [ { "family_name": "Cohen", "given_name": "Marshall H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" } ], "contributor": [ { "family_name": "Miller", "given_name": "H. Richard", "clpid": "Miller-H-R" }, { "family_name": "Wiita", "given_name": "Paul J.", "clpid": "Wiita-P-J" } ], "abstract": "In this review I concentrate on three features of the small-scale structure of radio sources: their morphology and classification, the superluminal motion, and some statistics. Fortunately, a number of excellent review articles have appeared recently which bear on these and related topics, so my task is rather easy. I especially recommend the volumes Superluminal Radio Sources [1] and The Impact of VLBI on Astrophysics and Geophysics [2], both of which contain informative reviews as well as numerous short articles.", "doi": "10.1007/3-540-19492-4_211", "isbn": "9783540194927", "publisher": "Springer", "place_of_publication": "Berlin", "publication_date": "1988", "pages": "290-301" }, { "id": "authors:v4sx9-bcb68", "collection": "authors", "collection_id": "v4sx9-bcb68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200929-163431484", "type": "book_section", "title": "Superluminal Radio Sources", "book_title": "Extragalactic Radio Sources", "author": [ { "family_name": "Cohen", "given_name": "M. H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" }, { "family_name": "Unwin", "given_name": "S. C.", "clpid": "Unwin-S-C" } ], "contributor": [ { "family_name": "Heeschen", "given_name": "David S.", "clpid": "Heeschen-D-S" }, { "family_name": "Wade", "given_name": "Campbell M.", "clpid": "Wade-C-M" } ], "abstract": "Several compact radio sources studied with VLBI show apparent transverse velocities much greater than the speed of light. This review is a summary of VLBI observations of these \"superluminal\" sources as of August 1981. The physical models proposed to explain this phenomenon are also discussed.", "doi": "10.1007/978-94-009-7781-5_96", "isbn": "9789400977839", "publisher": "Springer Netherlands", "place_of_publication": "Dordrecht", "publication_date": "1982", "pages": "345-354" }, { "id": "authors:9jsfh-tb836", "collection": "authors", "collection_id": "9jsfh-tb836", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181121-090807122", "type": "book_section", "title": "Superluminal Expansion of 3C 273", "book_title": "Extragalactic Radio Sources", "author": [ { "family_name": "Pearson", "given_name": "T. J.", "orcid": "0000-0001-5213-6231", "clpid": "Pearson-T-J" }, { "family_name": "Unwin", "given_name": "S. C.", "clpid": "Unwin-S-C" }, { "family_name": "Cohen", "given_name": "M. H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" }, { "family_name": "Linfield", "given_name": "R. P.", "clpid": "Linfield-R-P" }, { "family_name": "Readhead", "given_name": "A. C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Seielstad", "given_name": "G. A.", "clpid": "Seielstad-G-A" }, { "family_name": "Simon", "given_name": "R. S.", "clpid": "Simon-R-S" }, { "family_name": "Walker", "given_name": "R. C.", "clpid": "Walker-R-C" } ], "contributor": [ { "family_name": "Heeschen", "given_name": "David S.", "clpid": "Heeschen-D-S" }, { "family_name": "Wade", "given_name": "C. M.", "clpid": "Wade-C-M" } ], "abstract": "Figure 1 shows hybrid maps of the core of 3C 273B at five epochs, made with arrays of 4 or 5 VLBI antennas. The maps span a period of 3.5 years. They all show a bright eastern peak and a lower-brightness extension to the west. There is a local maximum in the western extension between 6 and 8 milliarcsec from the main peak. This \"blob\" moves steadily further away from the main peak along a roughly straight line in PA \u2212116\u00b0 \u00b1 2\u00b0. Compare this with the position angle of the 25-arcsec optical jet, \u2212137\u00b0. The maps show a slight curvature to the south with increasing separation from the main peak. Lower-resolution VLBI maps at lower frequencies show that this curvature continues at greater separations, suggesting a smooth connection between the milli-arcsecond position angle and the position angle of the optical jet. In our latest map (1981.09) the blob is no longer detectable with the limited dynamic range of the VLBI network (about 20:1).", "doi": "10.1017/S0074180900028126", "isbn": "9789027713841", "publisher": "D. Reidel", "place_of_publication": "Dordrecht", "publication_date": "1982", "pages": "355-356" }, { "id": "authors:grqh4-n8t64", "collection": "authors", "collection_id": "grqh4-n8t64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170810-170220457", "type": "book_section", "title": "Very-long-baseline interferometry experiments", "author": [ { "family_name": "Cohen", "given_name": "M. H.", "orcid": "0000-0002-8033-5972", "clpid": "Cohen-M-H" } ], "abstract": "VLB observations have been made at many wavelengths from 2.8 to 270 cm. The highest resolution was obtained on the Greenbank-Crimea baseline, 2.9 x 10^8 wavelengths long at 2.8 cm on which two quasars showed interference fringes. The observations between Goldstone, California and Canberra, Australia (8.1 x 10^7 wavelengths at 13 cm) were the most sensitive, with a minimum detectable flux of 0.3 f.u. These gave fringes on 56 sources, and there are sufficient data to calibrate the interferometer and derive accurate positions, based on time delay and fringe rate. Typical accuracy is two seconds of arc. At 270 cm observations were made on the baselines Owens Valley-Greenbank-Arecibo. Three sources showed fringes. Preliminary values for the diameters are in rough agreement with values expected from the theory of interstellar scintillations.", "doi": "10.1109/APS.1970.1150838", "publisher": "IEEE", "publication_date": "1970-09" } ]