Moderate-luminosity growing black holes from 1.25<z<2.7 : varied accretion in disk-dominated hosts

Simmons, B. D. and Urry, C. M. and Schawinski, K. and Cardamone, C. and Glikman, E. (2012) Moderate-luminosity growing black holes from 1.25<z<2.7  : varied accretion in disk-dominated hosts. The Astrophysical Journal, 761 (1): 75. ISSN 0004-637X

Abstract

We compute black hole masses and bolometric luminosities for 57 active galactic nuclei (AGNs) in the redshift range 1.25 ≤ z ≤ 2.67, selected from the GOODS-South deep multi-wavelength survey field via their X-ray emission. We determine host galaxy morphological parameters by separating the galaxies from their central point sources in deep Hubble Space Telescope images, and host stellar masses and colors by multi-wavelength spectral energy distribution fitting. Of GOODS AGNs at these redshifts, 90% have detected rest-frame optical nuclear point sources; bolometric luminosities range from 2 × 1043 to 2 × 1046 erg s–1. The black holes are growing at a range of accretion rates, with gsim 50% of the sample having L/L Edd < 0.1. Of the host galaxies, 70% have stellar masses M * > 1010 M ☉, with a range of colors suggesting a complex star formation history. We find no evolution of AGN bolometric luminosity within the sample, and no correlation between AGN bolometric luminosity and host stellar mass, color, or morphology. Fully half the sample of host galaxies are disk-dominated, with another 25% having strong disk components. Fewer than 15% of the systems appear to be at some stage of a major merger. These moderate-luminosity AGN hosts are therefore inconsistent with a dynamical history dominated by mergers strong enough to destroy disks, indicating that minor mergers or secular processes dominate the coevolution of galaxies and their central black holes at z ~ 2.