Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/68139

Title

AEGIS: the color-magnitude relation for X-ray-selected active galactic nuclei

Author(s)

Nandra, Kirpal;  Georgakakis, Antonis;  Willmer, Christopher N.;  Cooper, Michael C.;  Croton, D. J.;  Davis, Michael A.;  Faber, S. M.;  Koo, David C.;  Laird, Elise S.;  Newman, Jeffrey A.

Abstract

We discuss the relationship between rest-frame color and optical luminosity for X-ray sources in the range 0.6 < z < 1.4 selected from the Chandra survey of the Extended Groth Strip. These objects are almost exclusively active galactic nuclei (AGNs). While there are a few luminous QSOs, most are relatively weak or obscured AGNs whose optical colors should be dominated by host galaxy light. The vast majority of AGN hosts at z ∼ 1 are luminous and red, with very few objects fainter than MB = -20.5 or bluer than U - B = 0.6. This places the AGNs in a distinct region of color-magnitude space, on the 'red sequence' or at the top of the 'blue cloud,' with many in between these two modes in galaxy color. A key stage in the evolution of massive galaxies is when star formation is quenched, resulting in a migration from the blue cloud to the red sequence. Our results are consistent with scenarios in which AGNs either cause or maintain this quenching. The large number of red-sequence AGNs implies that strong, ongoing star formation is not a necessary ingredient for AGN activity, as black hole accretion appears often to persist after star formation has been terminated.

Publication type

Journal article

Source

Astrophysical Journal Letters, Vol. 660, no. 1 (May 2007), pp. L11-L14

Publication year

2007

FOR Code(s)

0201 Astronomical and Space Sciences

Keyword(s)

Active galaxies;  Galaxies;  Galaxy evolution;  Optical luminosity;  Rest-frame color;  X-rays

Publisher

University of Chicago Press

ISSN

0004-637X

Publisher URL

http://dx.doi.org/10.1086/517918

Copyright

Copyright © 2007 The American Astronomical Society. All rights reserved. The American Astronomical Society does not allow institutions to archive either the accepted manuscript or the published version of the article. However, you can find an earlier version of the full text here: http://arxiv.org/abs/astro-ph/0607270.

Peer reviewed