Morphological and color characteristics of active galactic nucleus host galaxies at Z ∼ 1

This thesis investigates the color and morphology characteristics of galaxies at 0.2 < z < 1.2 hosting active galactic nuclei (AGNs). The AGNs presented here are selected by X-ray luminosities, radio powers, and/or optical spectra signatures, using extensive multiwavelength data from two complementary surveys, the All-wavelength Extended Groth Strip Interational Survey (AEGIS) and the northern field of the Great Observatories Origins Deep Survey (GOODS-N); control samples are also selected from these data. Compared to the control samples, AGN host galaxies are more often morphologically classified as interacting or E/S0/Sa (or early-type) at less than a 2sigma level of significance, which only mildly suggests that they are currently interacting or may have undergone a merger in the past. However, galaxies hosting X-ray-selected AGNs are less often classified as Sb-Ir than the control galaxies at a level of significance greater than 2sigma. The rates of incidence of kinematically close companions are generally consistent between AGN hosts and control galaxies, potentially restricting the initial start of significant nuclear activity to well into the interaction. Optical and UV-optical host galaxy colors depend on the AGN sample, with the majority of AGN host galaxies being identified as red or green; an exception to this trend is a pair of broad-line AGNs whose hosts are classified as blue. Simulations designed to test the reliability of the color and morphology measurements used here indicate that the measurements are potentially sensitive to low-luminosity contributions from unobscured AGNs (e.g., quasars) but that such AGNs should be visibly identifiable as optical point sources. Thus these systems can be flagged and analyzed separately.