AEGIS: Host Galaxy Morphologies of X-Ray-selected and Infrared-selected Active Galactic Nuclei at 0.2 ≤ z < 1.2

We visually and quantitatively determine the host galaxy morphologies of 94 intermediate-redshift (0.2 ≤ z < 1.2) active galactic nuclei (AGNs), selected using Chandra X-ray data and Spitzer mid-infrared data in the Extended Groth Strip. Using recently developed morphology measures, the second-order moment of the brightest 20% of a galaxy's flux (M20) and the Gini coefficient, we find that X-ray-selected AGNs mostly reside in E/S0/Sa galaxies (53%), while IR-selected AGNs show no clear preference for host morphology. X-ray-selected AGN hosts are members of close pairs more often than the field population by a factor of 3.3 ± 1.4, but most of these pair members appear to be undisturbed early-type galaxies and do not tend to show direct evidence of gravitational perturbations or interactions. Thus, the activation mechanism for AGN activity remains unknown, even for pair members.