A Caltech Library Service

Observational Evidence for the Coevolution of Galaxy Mergers, Quasars, and the Blue/Red Galaxy Transition

Hopkins, Philip F. and Bundy, Kevin and Hernquist, Lars and Ellis, Richard S. (2007) Observational Evidence for the Coevolution of Galaxy Mergers, Quasars, and the Blue/Red Galaxy Transition. Astrophysical Journal, 659 (2). pp. 976-996. ISSN 0004-637X. doi:10.1086/512091.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


We compile a number of observations to estimate the time-averaged rate of formation or buildup of red sequence galaxies, as a function of mass and redshift. Comparing this with the mass functions of mergers and quasar hosts, and independently comparing their clustering properties as a function of redshift, we find that these populations trace the same mass distribution, with similar evolution, at redshifts 0 < z ≾ 1.5. Knowing one of the quasar, merger, or elliptical mass/luminosity functions, it is possible to predict the others. Allowing for greater model dependence, we compare the rate of early-type buildup with the implied merger and quasar triggering rates as a function of mass and redshift and find agreement. Over this redshift range, observed merger fractions can account for the entire bright quasar luminosity function and buildup of the red sequence at all but the highest masses at low redshift (≳ 10^(11) M_⊙ at z ≾ 0.3) where "dry" mergers appear to dominate. This supports a necessary prediction of theories where mergers between gas-rich galaxies produce ellipticals with an associated phase of quasar activity, after which the remnant becomes red. These populations trace a similar characteristic transition mass, possibly reflecting the mass above which the elliptical population is mostly (≳50%) assembled at a given redshift, which increases with redshift over the observed range in a manner consistent with suggestions that cosmic downsizing may apply to red galaxy assembly as well as star formation. These mass distributions as a function of redshift do not uniformly trace the all/red/blue galaxy population, ruling out models in which quasar activity is generically associated with star formation or is long lived in "old" systems.

Item Type:Article
Related URLs:
URLURL TypeDescription
Hopkins, Philip F.0000-0003-3729-1684
Bundy, Kevin0000-0001-9742-3138
Hernquist, Lars0000-0001-6950-1629
Ellis, Richard S.0000-0001-7782-7071
Additional Information:© 2007 The American Astronomical Society. Received 2006 May 22; accepted 2006 December 14. We thank Eric Bell, Arjun Dey, David Hogg, Casey Papovich, Rachel Somerville, Stijn Wuyts, Sandy Faber, and Marijn Franx for very helpful discussions. We also thank T. J. Cox, Brant Robertson, and the anonymous referee, whose comments improved this manuscript. This work was supported in part by NSF grants ACI 96-19019, AST 00-71019, AST 02-06299, and AST 03-07690 and NASA ATP grants NAG5-12140, NAG5-13292, and NAG5-13381.
Funding AgencyGrant Number
NSFACI 96-19019
NSFAST 00-71019
NSFAST 02-06299
NSFAST 03-07690
Subject Keywords:cosmology : theory; galaxies : active; galaxies : evolution; quasars : general
Issue or Number:2
Record Number:CaltechAUTHORS:20091112-122300293
Persistent URL:
Official Citation:Observational Evidence for the Coevolution of Galaxy Mergers, Quasars, and the Blue/Red Galaxy Transition Philip F. Hopkins, Kevin Bundy, Lars Hernquist, and Richard S. Ellis 2007 ApJ 659 976-996 doi: 10.1086/512091
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16688
Deposited By: Tony Diaz
Deposited On:23 Nov 2009 21:59
Last Modified:08 Nov 2021 23:29

Repository Staff Only: item control page