AGN-host connection at 0.5 < z < 2.5: A rapid evolution of AGN fraction in red galaxies during the last 10 Gyr

¹ Laboratoire AIM-Paris-Saclay, CEA/DSM/Irfu, CNRS, Université Paris Diderot, Saclay, pt courrier 131, 91191 Gif-sur-Yvette, France
e-mail: taowang@nju.edu.cn
² Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, School of Astronomy & Space Science, Nanjing University, Nanjing 210093, PR China
³ Department of Physics, Durham University, South Road, Durham DH1 3LE, UK
⁴ CAS Key Laboratory for Researches in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Chinese Academy of Sciences, Hefei, Anhui 230026, PR China
⁵ Leiden Observatory, Leiden University, 2300 RA Leiden, The Netherlands
⁶ Purple Mountain Observatory, Chinese Academy of Sciences, 2 West-Beijing Road, Nanjing 210008, PR China
⁷ Department of Physics, University of Bath, Claverton Down, Bath, BA2 7AY, UK
⁸ Department of Physics, Anhui Normal University, Wuhu, Anhui 241000, PR China
⁹ Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003, PR China
¹⁰ National Astronomical Observatories of China, Chinese Academy of Sciences, Beijing 100012, PR China
¹¹ Harvard-Smithsonian Center for Astrophysics, 60 Garden Str., Cambridge, MA 02138, USA

Received: 1 June 2015
Accepted: 11 January 2017

Abstract

We explore the dependence of the incidence of moderate-luminosity (L_{0.5−8 keV} = 10^41.9−43.7 erg s^-1) active galactic nuclei (AGNs) and the distribution of their accretion rates on host color at 0.5 <z < 2.5. Based on the deepest X-ray and UV-to-far-infrared data in the two The Great Observatories Origins Deep Survey (GOODS) fields, we identify 221 AGNs within a mass-complete parent galaxy sample down to M_∗ > 10¹⁰ M_⊙. We use extinction-corrected rest-frame U−V colors to divide both AGN hosts and non-AGN galaxies into red sequence (red), green valley (green), and blue cloud (blue) populations. We find that the fraction of galaxies hosting an AGN at fixed X-ray luminosity increases with stellar mass and redshift for all the three galaxy populations, independent of their colors. However, both the AGN fraction at fixed stellar mass and its evolution with redshift are clearly dependent on host colors. Most notably, red galaxies have the lowest AGN fraction (~5%) at z ~ 1 yet with most rapid evolution with redshift, increasing by a factor of ~5 (24%) at z ~ 2. Green galaxies exhibit the highest AGN fraction across all redshifts, which is most pronounced at z ~ 2 with more than half of them hosting an AGN at M_∗ > 10^10.6 M_⊙. Together with the high AGN fraction in red galaxies at z ~ 2, this indicates that (X-ray) AGNs could be important in both transforming (quenching) star-forming galaxies into quiescent ones and subsequently maintaining their quiescence at high redshift. Furthermore, consistent with previous studies at lower redshifts, we show that the probability of hosting an AGN for the total galaxy population can be characterized by a universal Eddington ratio (as approximated by L_X/M_∗) distribution (p(λ_Edd) ~ λ_Edd^-0.4), which is independent on host mass. Yet consistent with their different AGN fractions, galaxies with different colors appear to also have different p(λ_Edd) with red galaxies exhibiting more rapid redshift evolution compared with that for green and blue galaxies. Evidence for a steeper power-law distribution of p(λ_Edd) in red galaxies (p(λ_Edd) ~ λ_Edd^-0.6) is also presented, though larger samples are needed to confirm. These results suggest that the AGN accretion or the growth of supermassive black holes is related to their host properties, and may also influence their hosts in a different mode dependent on the host color.