All-wavelength Extended Groth strip International Survey: the environment of X-ray sources at z~1
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All-wavelength Extended Groth strip International Survey: the environment of X-ray sources at z~1

  • Author(s): Georgakakis, A
  • Nandra, K
  • Laird, ES
  • Cooper, MC
  • Gerke, BF
  • Newman, JA
  • Croton, DJ
  • Davis, M
  • Faber, SM
  • Coil, AL
  • et al.

Published Web Location

https://arxiv.org/pdf/astro-ph/0607274v1.pdf
No data is associated with this publication.
Abstract

We explore the environment of z~1 AGN using a sample of 53 spectroscopically identified X-ray sources in the All-wavelength Extended Groth strip International Survey. We quantify the local density in the vicinity of an X-ray source by measuring the projected surface density of spectroscopically identified optical galaxies within a radius defined by the 3rd nearest neighbour. Our main result is that X-ray selected AGN at z~1 avoid underdense regions at the 99.89% confidence level. Moreover, although we find that the overall population shares the same (rich) environment with optical galaxies of similar U-B and M_B, there is also tentative evidence (96%) that AGN with blue colors (U-B<1) reside in denser environments compared to optical galaxies. We argue that the results above are a consequence of the whereabouts of massive galaxies, capable of hosting supermassive black holes at their centers, with available cold gas reservoirs, the fuel for AGN activity. At z~1 an increasing fraction of such systems are found in dense regions.

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