We present the rest-frame optical morphologies of active galactic nucleus (AGN) host galaxies at 1.5 < z < 3, using near-infrared imaging from the Hubble Space Telescope Wide Field Camera 3, the first such study of AGN host galaxies at these redshifts. The AGNs are X-ray-selected from the Chandra Deep Field South and have typical luminosities of 1042 erg s-1<L X < 1044 erg s-1. Accreting black holes in this luminosity and redshift range account for a substantial fraction of the total space density and black hole mass growth over cosmic time; they thus represent an important mode of black hole growth in the universe. We find that the majority (∼80%) of the host galaxies of these AGNs have low Sérsic indices indicative of disk-dominated light profiles, suggesting that secular processes govern a significant fraction of the cosmic growth of black holes. That is, many black holes in the present-day universe grew much of their mass in disk-dominated galaxies and not in early-type galaxies or major mergers. The properties of the AGN host galaxies are furthermore indistinguishable from their parent galaxy population and we find no strong evolution in either effective radii or morphological mix between z ∼ 2 and z ∼ 0.05.
Bibliographical noteFunding Information:
Support for the work of K.S. and E.T. was provided by NASA through Einstein/Chandra Postdoctoral Fellowship grant numbers PF9-00069 and PF8-90055, respectively, issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. C.M.U. and C.C. acknowledge support from NSF grants AST-0407295, AST-0449678, AST-0807570, and Yale University. S.K.Y. acknowledges the support by the National Research Foundation of Korea through the Doyak grant (No. 20090078756) and the SRC grant to the Center for Galaxy Evolution Research. K.S. is grateful for the hospitality of the Astronomy Department at Yonsei University, Korea and thanks Yun-Kyeong Sheen, Sang-Il Han, and Andrew Fruchter for technical help. This research has made use of NASA’s Astrophysics Data System Bibliographic Services. Facilities: HST (WFC3), CXO (ACIS)
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All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science