Obscured goods active galactic nuclei and their host galaxies at z <1.25 : the slow black hole growth phase

Simmons, B. D. and Van Duyne, J. and Urry, C. M. and Treister, E. and Koekemoer, A. M. and Grogin, N. A. (2011) Obscured goods active galactic nuclei and their host galaxies at z <1.25 : the slow black hole growth phase. The Astrophysical Journal, 734 (2): 121. ISSN 0004-637X

Abstract

We compute black hole masses and bolometric luminosities for 87 obscured active galactic nuclei (AGNs) in the redshift range 0.25 ≤ z ≤ 1.25, selected from the GOODS deep multi-wavelength survey fields via their X-ray emission. We fit the optical images and obtain morphological parameters for the host galaxy, separating the galaxy from its central point source, thereby obtaining a four-band optical spectral energy distribution (SED) for each active nucleus. We calculate bolometric luminosities for these AGNs by reddening a normalized mean SED of GOODS broad-line AGNs to match the observed central point-source SED of each obscured AGN. This estimate of L bol has a smaller spread than simple bolometric corrections to the X-ray luminosity or direct integration of the observed multi-wavelength SED, suggesting it is a better measure. We estimate central black hole masses from the bulge luminosities. The black hole masses span a wide range, 7 × 106 M ☉ to 6 × 109 M ☉; the median black hole mass is 5 × 108 M ☉. The majority of these AGNs have L/L Edd ≤ 0.01, and we detect no significant evolution of the mean Eddington ratio to z = 1.25. This implies that the bulk of black hole growth in these obscured AGNs must have occurred at z gsim 1 and that we are observing these AGNs in a slow- or no-growth state.