Optical colours of AGN in the Extended Chandra Deep Field South: Obscured black holes in early type galaxies

Abstract

We investigate the optical colours of X-ray sources from the Extended Chandra Deep Field South (ECDFS) using photometry from the COMBO-17 survey, aiming to explore AGN - galaxy feedback models. The X-ray sources populate both the ``blue'' and the ``red sequence'' on the colour-magnitude diagram. However, sources in the ``red sequence'' appear systematically more obscured. HST imaging from the GEMS survey demonstrates that the nucleus does not affect significantly the observed colours, and therefore red sources are early-type systems. In the context of AGN feedback models, this means that there is still remaining material after the initial ``blowout''. We argue that this material could not be only left-over from the original merger, but a secondary cold gas supplier (such as minor interactions or self-gravitational instabilities) must also assist.

Submitted to A&A

References in corpus (3)

• An Observational Determination of the Bolometric Quasar Luminosity Function
• AEGIS: The color-magnitude relation for X-ray selected AGN
• XMM and Chandra measurements of the AGN intrinsic absorption: dependence on luminosity and redshift

Cited by in corpus (5)

• Cosmic X-ray Surveys of Distant Active Galaxies: The Demographics, Physics, and Ecology of Growing Supermassive Black Holes
• The role of AGN in the colour transformation of galaxies at redshifts z~1
• Searching for mid-IR obscured AGN in the CDF-N
• The relation between AGN type and host galaxy properties
• The XMM-Newton survey in the H-ATLAS field