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The Astrophysical Journal Volume 693 Number 2 Create an alert RSS this journal

Ezequiel Treister et al. 2009 ApJ 693 1713 doi:10.1088/0004-637X/693/2/1713

OPTICAL SPECTROSCOPY OF X-RAY SOURCES IN THE EXTENDED CHANDRA DEEP FIELD SOUTH* **

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Ezequiel Treister1,2,9, Shanil Virani3, Eric Gawiser4, C. Megan Urry3,5, Paulina Lira6, Harold Francke6, Guillermo A. Blanc7, Carolin N. Cardamone3, Maaike Damen8, Edward N. Taylor8 and Kevin Schawinski3

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Abstract References Cited By

We present the first results of our optical spectroscopy program aimed to provide redshifts and identifications for the X-ray sources in the Extended Chandra Deep Field South. A total of 339 sources were targeted using the IMACS spectrograph at the Magellan telescopes and the VIMOS spectrograph at the VLT. We measured redshifts for 186 X-ray sources, including archival data and a literature search. We find that the active galactic nucleus (AGN) host galaxies have on average redder rest-frame optical colors than nonactive galaxies, and that they live mostly in the "green valley." The dependence of the fraction of AGNs that are obscured on both luminosity and redshift is confirmed at high significance and the observed AGN spatial density is compared with the expectations from existing luminosity functions. These AGNs show a significant difference in the mid-IR to X-ray flux ratio for obscured and unobscured AGNs, which can be explained by the effects of dust self-absorption on the former. This difference is larger for lower luminosity sources, which is consistent with the dust opening angle depending on AGN luminosity.


Footnote
*  This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.
Footnote
**  Partly based on observations collected at the European Southern Observatory, Chile, under programs 078.A-0485 and 072.A-0139.
Keywords

galaxies: active; quasars: general; X-rays: galaxies


Dates

Issue 2 (2009 March 10)

Received 2008 July 7, accepted for publication 2008 December 10

Published 2009 March 10



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