The cosmological x-ray evolution of stars, AGN, and galaxies

It is of great importance for our understanding of galaxy evolution to determine whether there is a break or a continuum in these processes from the powerful quasars and starbursts of the past, to the seemingly dormant, "normal" galaxies more typical of the present epoch. To help settle the question, we combined optical data from the NOAO Deep Wide-Field Survey (NDWFS), X-ray data from the XBootes survey, and spectral information from the AGN and Galaxy Evolution Survey (AGES) in order to simultaneously obtain deep and wide coverage of the normal galaxy population. In this manner, my collaborators and I were able to bridge the gap in normal galaxy X-ray coverage between large-area local surveys and high redshift, small volume deep fields. In particular, I present the X-ray evolution of normal galaxies as a function of absolute optical luminosity, redshift, and spectral type over the largely unexplored redshift range 0 ≲ z ≲ 0.5. We use radial emission profiles of low redshift galaxies, hardness ratios, and X-ray to optical luminosity ratios to estimate the relative contributions of stellar and nuclear sources. These tests suggest that the X-ray emission from spectroscopically late-type galaxies is dominated by star formation, while that from early-type galaxies is dominated by AGN.;To extend our analysis of AGN to higher redshifts, we investigated the X-ray luminosity evolution of 3316 red galaxies selected over a wide range in redshift (0.3 < z < 0.9) from a 1.4 deg2 region of the XBootes field. As in our lower redshift study, we find that the mean X-ray luminosity increases as a function of redshift like ∼ (1 + z)4. In combination with the similar trends observed for more luminous AGN, these results also indicate that the global decline in accretion onto the central, supermassive black holes of early-type galaxies has proceeded in a similar manner at both the faint and the bright (individually detectable) ends of the AGN luminosity function. (Abstract shortened by UMI.)...