Mathematics – Logic
Scientific paper
Dec 2000
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000phdt.........3n&link_type=abstract
Thesis (PhD). UNIVERSITY OF PENNSYLVANIA, Source DAI-B 61/06, p. 3093, Dec 2000, 179 pages.
Mathematics
Logic
Scientific paper
We present three separate studies on methods to quantify the composition of the energy density of the universe. First, we analyze the calculation of the rate of microlensing events towards the bulge of the Milky Way. We show that the contribution to the lensing optical depth due to sources in the disk behind the bulge of our galaxy may be as high as 15% of the total optical depth towards the bulge, of which about half comes from stars farther than 3kpc behind the bulge. We explore the possible disk structure behind the bulge, analyzing the effects of the collision of the Sagittarius dwarf galaxy with the Milky Way and also possible warping and flaring of the disk. Next, we study a method to constrain the cosmological constant, based on the fact that the shape of the contours of the correlation function of the galaxies in redshift space depends upon the background cosmology, and in particular on the cosmological constant. We find that the population of Lyman-break galaxies, at high redshifts and with a large bias in their clustering compared to the underlying matter distribution, is an ideal population to which this method can be applied. We discuss the survey that is required to make this measurement using this method, given the surface density of these galaxies that are currently observed, the shot noise and the cosmic variance. Finally, we study the strong gravitational lensing of radio and optical sources. We analyze the statistics of lensing taking into account for the first time the effect of the clustering of galaxies. We show that the dark matter in halos that is not bound to galaxies boost the image separations by 30%. Due to this effect, we expect a significant optical depth to lensing from galaxies in small groups and clusters. We show that the number of large separation lenses expected in our model is consistent with the number observed in CLASS and HST snap-shot surveys. We also show that the typical shear expected from the clustering effect is large (~0.1).
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