Mathematics – Logic
Scientific paper
Oct 1997
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1997phdt.........7r&link_type=abstract
Thesis (PHD). COLUMBIA UNIVERSITY , Source DAI-B 58/04, p. 1926, Oct 1997, 163 pages.
Mathematics
Logic
1
Gravitational Lensing
Scientific paper
Cosmological backgrounds can be decomposed into a component originating from diffuse emission, and one produced by a collection of discrete sources. The object of the present thesis is the study of the properties of the discrete component and the exploration of several of its cosmological applications. In chapter 1, an overview of the study of discrete-source backgrounds is presented. In addition, a description of the cosmic X-ray and radio-source backgrounds, of the effect of gravitational lensing by clusters, and of the Sunyaev-Zel'dovich effect is provided. The soft X-Ray Background is now known to originate primarily from discrete sources. In chapter 2, we study the two-point correlation function between the X-Ray Background and galaxy catalogs, and develop a direct two-dimensional formalism to interpret its angular dependence. This allows us to measure the mean X-ray flux of optical galaxies and to probe faint diffuse X-ray emission. Gravitational lensing can affect extragalactic backgrounds by altering the apparent density and flux distributions of their constituting sources. In chapter 3, the effect of gravitational lensing by clusters of galaxies on the X-Ray background is discussed. By considering the particular case of the cluster A1689, we show that the lensing-induced depletion in the number of detectable sources should be observable by the future X-ray mission AXAF. In chapter 4, we show that gravitational lensing causes a systematic deficit in the residual intensity of the radio-source background, after subtraction of detectable sources. If not corrected for, this can lead to an overestimation of the Sunyaev-Zel'dovich temperature decrement in the Cosmic Microwave Background, and to an underestimation of subsequent determination of the Hubble constant. Conclusions and natural extensions of this thesis are summarized in chapter 5.
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