AGN UNIFICATION AT z ∼ 1: u − R COLORS AND GRADIENTS IN X-RAY AGN HOSTS

We present uncontaminated rest-frame u − R colors of 78 X-ray-selected active galactic nucleus (AGN) hosts at 0.5 < z < 1.5 in the Chandra Deep Fields measured with Hubble Space Telescope (HST)/Advanced Camera for Surveys/NICMOS and Very Large Telescope/ISAAC imaging. We also present spatially resolved NUV − R color gradients for a subsample of AGN hosts imaged by HST/Wide Field Camera 3 (WFC3). Integrated, uncorrected photometry is not reliable for comparing the mean properties of soft and hard AGN host galaxies at z ∼ 1 due to color contamination from point-source AGN emission. We use a cloning simulation to develop a calibration between concentration and this color contamination and use this to correct host galaxy colors. The mean u − R color of the unobscured/soft hosts beyond ∼6 kpc is statistically equivalent to that of the obscured/hard hosts (the soft sources are 0.09 ± 0.16 mag bluer). Furthermore, the rest-frame V − J colors of the obscured and unobscured hosts beyond ∼6 kpc are statistically equivalent, suggesting that the two populations have similar distributions of dust extinction. For the WFC3/infrared sample, the mean NUV − R color gradients of unobscured and obscured sources differ by less than ∼0.5 mag for r > 1.1 kpc. These three observations imply that AGN obscuration is uncorrelated with the star formation rate beyond ∼1 kpc. These observations favor a unification scenario for intermediate-luminosity AGNs in which obscuration is determined geometrically. Scenarios in which the majority of intermediate-luminosity AGNs at z ∼ 1 are undergoing rapid, galaxy-wide quenching due to AGN-driven feedback processes are disfavored.

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