X-Ray Selected AGN Host Galaxies are Similar to Inactive Galaxies out to z = 3: Results from CANDELS/CDF-S

We use multi-band spatially resolved photometry from the Cosmic Assembly Near-IR Deep Legacy Survey in the 4 Ms Chandra Deep Field-South to explore the nuclear and extended colors, color gradients, and stellar populations of the host galaxies of X-ray selected active galactic nuclei (AGNs) out to z = 3. Based on a study of their central light, we develop X-ray based criteria to exclude objects with strong AGN contamination. We use stellar masses from the FIREWORKS database to understand and account for stellar mass selection effects and carefully study, for the first time, the resolved host galaxy properties of AGNs at z ~ 2 in their rest-frame optical light without substantial nuclear contamination. AGN hosts span a sizable range of stellar masses, colors, and color gradients at these redshifts. Their colors, color gradients, and stellar population properties are very similar to inactive galaxies of the same stellar mass. At z ~ 1, we find a slightly narrower range in host colors compared to inactive galaxies, as well as hints of more recent star formation. These differences are weaker or non-existent among AGN hosts at z ~ 2. We discuss the importance of AGN-driven feedback in the quenching of galaxies at z >~ 1 and speculate on possible evolution in the relationship between black hole accretion and the host galaxy toward high redshifts.