Mathematics – Logic
Scientific paper
Oct 1998
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1998phdt........26c&link_type=abstract
Thesis (PHD). COLUMBIA UNIVERSITY , Source DAI-B 59/07, p. 3492, Jan 1999, 121 pages.
Mathematics
Logic
Cosmology, First, Dark Matter, Galaxy Clusters
Scientific paper
In this thesis we investigate cosmological information that can be extracted from celestial observations at radio wavelengths. Most of the investigation uses a catalog of extragalactic, radio-loud objects observed in a 1.4 GHz survey called FIRST (Faint Images of the Radio Sky at Twenty centimeters). The technical aspects involved in the statistical analysis of galaxy clustering are discussed and appropriate methods are applied to various samples of the FIRST data. We go on to develop the general formalism required to interpret, within a standard cosmological framework, clustering measurements made in deep two-dimensional surveys. The FIRST results are then combined with other clustering measurements to yield constraints on bias-the relationship between the clustering of luminous objects and mass in the universe. The sensitivity of clustering measurements to other cosmological parameters is also demonstrated. Having discussed the bias-related difficulties involved in testing standard theories of structure formation from clustering measurements, we move on to investigate the possibility of using the coherent distortions (weak lensing) of background FIRST sources by foreground matter to constrain directly the power spectrum of mass fluctuations in the universe (thus eliminating uncertainties associated with bias). We establish that the weak lensing signal is potentially detectable in a survey with the parameters of FIRST, and could yield a measurement of the dark matter power spectrum on 1o scales. Finally, the definition of 'radio sources' is stretched to include the negative Sunyaev-Zeldovich features produced at radio wavelengths when clusters of galaxies are viewed against the cosmic microwave background. We present the results of a Ryle Telescope observation of a decrement originally observed with the Very Large Array, and discuss the possibility that the data indicate the presence of a high-redshift cluster of galaxies. The number of clusters (peaks in the density fluctuations) detectable in this way is very sensitive to the density parameter Ω0 and the data provide a strong constraint on Ω0 if the S-Z interpretation is correct. The thesis concludes with a summary of the new cosmological information that has been extracted from radio observations.
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