[
{
"id": "thesis:6367",
"collection": "thesis",
"collection_id": "6367",
"cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05022011-085219561",
"primary_object_url": {
"basename": "Halverson_nw_2002.pdf",
"content": "final",
"filesize": 38458756,
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"url": "/6367/1/Halverson_nw_2002.pdf",
"version": "v5.0.0"
},
"type": "thesis",
"title": "A Measurement of the Cosmic Microwave Background Angular Power Spectrum with DASI",
"author": [
{
"family_name": "Halverson",
"given_name": "Nils William",
"clpid": "Halverson-Nils-William"
}
],
"thesis_advisor": [
{
"family_name": "Carlstrom",
"given_name": "John E.",
"clpid": "Carlstrom-J-E"
}
],
"thesis_committee": [
{
"family_name": "Vahala",
"given_name": "Kerry J.",
"orcid": "0000-0003-1783-1380",
"clpid": "Vahala-K-J"
},
{
"family_name": "Carlstrom",
"given_name": "John E.",
"clpid": "Carlstrom-J-E"
},
{
"family_name": "Johnson",
"given_name": "William Lewis",
"clpid": "Johnson-W-L"
},
{
"family_name": "Lange",
"given_name": "Andrew E.",
"clpid": "Lange-A-E"
},
{
"family_name": "Phillips",
"given_name": "Thomas G.",
"clpid": "Phillips-T-G"
},
{
"family_name": "Readhead",
"given_name": "Anthony C. S.",
"orcid": "0000-0001-9152-961X",
"clpid": "Readhead-A-C-S"
}
],
"local_group": [
{
"literal": "div_eng"
}
],
"abstract": "The Cosmic Microwave Background (CMB) has long been recognized as an astounding source of information about the early Universe. In this thesis we describe the design,\r\nimplementation, and first-year results of the Degree Angular Scale Interferometer (DASI), a compact interferometer designed to measure the angular power spectrum of the CMB. We discuss details of the optics, receivers, and power spectrum analysis, including the use of constraint matrices to project out contaminants and test for correlations with diffuse foreground templates.\r\n\r\nWe present a measurement of the CMB angular power spectrum in the multipole range l \u2248 100- 900 in nine bands. The measured fluctuations have a temperature spectral index of \u03b2 = -0.1 \u00b1 0.2 (1\u03c3) consistent with CMB. We find no evidence of foregrounds other than point sources in the data. We detect a first peak in the power spectrum at l ~ 200, a second peak in the power spectrum at l ~ 550, and a rise in the power spectrum at l ~ 800 which is indicative of a third, consistent with inflationary theories. \r\n\r\nUsing the DASI measurement along with COBE DMR data, and adopting conservative priors on the Hubble parameter h > 0.45 and an optical depth due to reionization 0.0 \u2264 \u03c4_c \u2264 0.4, we constrain the total density of the Universe \u03a9_(tot) = 1.04 \u00b1 0.06, the spectral index of the primordial density fluctuations n_s = 1.01^(+0.08)_(-0.06), and the physical baryon density \u03a9_bh^2 = 0.022^(+0.004)_(-0.003) among others (all 68% confidence limits). These constraints are consistent with inflation and estimates of \u03a9_bh^2 from Big Bang Nucleosynthesis. With prior h = 0.72 \u00b1 0.08, we constrain the matter density \u03a9_m = 0.40 \u00b1 0.15, and the vacuum energy density \u03a9_\u039b = 0.60 \u00b1 0.15, indicating from CMB data the presence of dark matter and dark energy in the Universe.",
"doi": "10.7907/BEJN-HQ49",
"publication_date": "2002",
"thesis_type": "phd",
"thesis_year": "2002"
},
{
"id": "thesis:6008",
"collection": "thesis",
"collection_id": "6008",
"cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08252010-152734353",
"primary_object_url": {
"basename": "Grego_l_1999.pdf",
"content": "final",
"filesize": 5001936,
"license": "other",
"mime_type": "application/pdf",
"url": "/6008/1/Grego_l_1999.pdf",
"version": "v5.0.0"
},
"type": "thesis",
"title": "Galaxy cluster gas fractions from interferometric measurements of the Sunyaev-Zel'dovich effect",
"author": [
{
"family_name": "Grego",
"given_name": "Laura",
"clpid": "Grego-L"
}
],
"thesis_advisor": [
{
"family_name": "Carlstrom",
"given_name": "John E.",
"clpid": "Carlstrom-J-E"
}
],
"thesis_committee": [
{
"family_name": "Unknown",
"given_name": "Unknown"
}
],
"local_group": [
{
"literal": "Owens Valley Radio Observatory (OVRO)"
},
{
"literal": "div_pma"
}
],
"abstract": "Interferometric measurements of the Sunyaev-Zel'dovich effect toward 18 highly x-ray luminous galaxy clusters are presented. The observations were made using centimeter-wave receivers specifically constructed for these observations. The data were taken with the receivers mounted on the Owens Valley Radio Observatory and Berkeley-Illinois-Maryland Association millimeter arrays between 1994 and 1998. The interferometric data are used to determine the gas mass fraction in these clusters in a uniform method. The inteferometric data contain sufficient spatial information to derive models for the pressure distribution of the cluster gas. From these models, under the assumption that the gas is isothermal, the cluster gas masses are estimated and the total gravitating masses are inferred. The total gravitating mass measurement requires the additional assumption that the gas is in hydrostatic equilibrium with the cluster potential. The cluster gas temperatures are obtained from x-ray spectral observations or, in the few cases in which spectra were unavailable, estimated from x-ray luminosity-temperature relations in the literature. Since the experiment best measures the gas fraction within a fixed angular radius, the measured gas fractions are extrapolated to a fiducial radius, using a relation derived from published numerical simulations, to facilitate comparisons. The best estimate of the cluster gas fraction at \u03c4_(500), the radius at which the enclosed mean density is 500 times the critical density, is (0.071^(+0.010)_(-0.012))h^(-1)_(100) at 68% confidence. Under the assumption that clusters are fair samples of the universe, the mass composition in clusters at the virial radius should reflect the universal mass composition. The intracluster gas is the dominant component of a cluster's baryonic mass, and so the gas mass fraction is a good approximation of the baryon mass fraction. The baryon fraction in clusters, f_B, together with the universal baryon mass density, \u03a9_B, sets a limit on the universal mass density, in the standard cosmological paradigm: \u03a9_M = \u03a9_B/ f_B. The cluster gas fraction measurements presented here set an upper limit to the universal mass density: \u03a9_Mh_(100) \u2264 0.27^(+0.07)_(-0.06), at 68% confidence. We make our best estimate of the universal matter density, including with the gas fraction estimates of the baryonic mass contained in galaxies and the baryonic mass which failed to become bound during the cluster formation process: \u03a9_M = 0.29^(+0.08)_(-0.06) at 68% confidence for h = 0.7.",
"doi": "10.7907/acvg-2168",
"publication_date": "1999",
"thesis_type": "phd",
"thesis_year": "1999"
},
{
"id": "thesis:3598",
"collection": "thesis",
"collection_id": "3598",
"cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09172008-132123",
"primary_object_url": {
"basename": "Akeson_rl_1997.pdf",
"content": "final",
"filesize": 6431972,
"license": "other",
"mime_type": "application/pdf",
"url": "/3598/1/Akeson_rl_1997.pdf",
"version": "v3.0.0"
},
"type": "thesis",
"title": "Millimeter Interferometric Polarimetry of Magnetic Field Structure in Protostellar Condensations",
"author": [
{
"family_name": "Akeson",
"given_name": "Rachel Lynn",
"orcid": "0000-0001-9674-1564",
"clpid": "Akeson-Rachel-Lynn"
}
],
"thesis_advisor": [
{
"family_name": "Carlstrom",
"given_name": "John E.",
"clpid": "Carlstrom-J-E"
}
],
"thesis_committee": [
{
"family_name": "Unknown",
"given_name": "Unknown"
}
],
"local_group": [
{
"literal": "Owens Valley Radio Observatory (OVRO)"
},
{
"literal": "Astronomy Department"
},
{
"literal": "div_pma"
}
],
"abstract": "Images of the linearly polarized emission from magnetically aligned dust grains have been used to investigate the magnetic field structure in the dense environments of young stellar objects. These observations provide constraints for theoretical modeling on scales relevant to protostellar disks, envelopes and outflows. Adjustable reflecting polarizers were installed at the Owens Valley Radio Observatory millimeter array to allow observations of polarized emission.
\r\n\r\nPolarized emission was detected toward two young stellar objects NGC 1333/ IRAS 4A and IRAS 16293-2422. Both sources are highly embedded and considered among the youngest objects known. The strong sub-millimeter and millimeter fluxes indicate a large amount of circumstellar material which may correspond to the magnetically supported envelopes predicted by theoretical models. Toward IRAS 4A, the magnetic field direction implied by the polarization position angle is parallel to the bipolar molecular outflow. Radiative transfer models were calculated and the offset of the polarized emission toward red-shifted outflow is consistent with an hourglass field morphology in the envelope.
\r\n\r\nThe polarized emission toward IRAS 16293 is located between the two binary components. The magnetic field direction coincides with directions seen in one of the four outflow lobes. However, the field direction is perpendicular to the rotation axis of the circumbinary disk. Given the complicated outflow and circumbinary disk structure of the source, a simple model can not explain the implied magnetic field direction or the offset of the polarized emission from the total intensity.
\r\n\r\nObservations were also made of the Orion KL region, though no polarization was detected. The upper limit to the polarized emissions suggests that the decrease in polarization seen by single-dish surveys toward the high mass young stellar object IRc2, is not due to field tangling.
\r\n\r\nThe implications of significant polarized emission as detected in the envelopes of IRAS 4A and IRAS 16293 are considered for several alignment mechanisms. Alignment by paramagnetic relaxation of thermally rotating grains will not be efficient in these dense, warm regions, and some mechanism for suprathermal grain rotation may be necessary to explain the observations.
\r\n\r\nThese observations clearly demonstrate the power of interferometric millimeter polarimetry in the study of the role of magnetic fields in protostellar condensations.
\r\n",
"doi": "10.7907/RGCX-HK35",
"publication_date": "1997",
"thesis_type": "phd",
"thesis_year": "1997"
}
]