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The Extended Chandra Deep Field-South Survey: Optical Spectroscopy of Faint X-ray Sources with the VLT and Keck

Silverman, J. D. and Capak, P. (2010) The Extended Chandra Deep Field-South Survey: Optical Spectroscopy of Faint X-ray Sources with the VLT and Keck. Astrophysical Journal Supplement Series, 191 (1). pp. 124-142. ISSN 0067-0049.

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We present the results of a program to acquire high-quality optical spectra of X-ray sources detected in the Extended-Chandra Deep Field-South (E-CDF-S) and its central 2 Ms area. New spectroscopic redshifts, up to z = 4, are measured for 283 counterparts to Chandra sources with deep exposures (t ~ 2-9 hr per pointing) using multi-slit facilities on both VLT (VIMOS) and Keck (DEIMOS), thus bringing the total number of spectroscopically identified X-ray sources to over 500 in this survey field. Since our new spectroscopic identifications are mainly associated with X-ray sources in the shallower 250 ks coverage, we provide a comprehensive catalog of X-ray sources detected in the E-CDF-S including the optical and near-infrared counterparts, determined by a likelihood routine, and redshifts (both spectroscopic and photometric), that incorporate published spectroscopic catalogs, thus resulting in a final sample with a high fraction (80%) of X-ray sources having secure identifications. We demonstrate the remarkable coverage of the luminosity-redshift plane now accessible from our data while emphasizing the detection of active galactic nuclei (AGNs) that contribute to the faint end of the luminosity function (L_(0.5-8 keV) ~ 10^(43)-10^(44) erg s^(–1)) at 1.5 ≲ z ≲ 3 including those with and without broad emission lines. Our redshift catalog includes 17 type-2 QSOs at 1 ≲ z ≲ 3.5 that significantly increases such samples (2×). Based on our deepest (9 hr) VLT/VIMOS observation, we identify "elusive" optically faint galaxies (R_(mag) ~ 25) at z ~ 2-3 based upon the detection of interstellar absorption lines (e.g., O II+Si IV, C II], C IV); we highlight one such case, an absorption-line galaxy at z = 3.208 having no obvious signs of an AGN in its optical spectrum. In addition, we determine accurate distances to eight galaxy groups with extended X-ray emission detected both by Chandra and XMM-Newton. Finally, we measure the physical extent of known large-scale structures (z ~ 0.7) evident in the CDF-S. While a thick sheet (a radial size of 67.7 Mpc) at z ~ 0.67 extends over the full field, the z ~ 0.73 structure is thin (18.8 Mpc) and filamentary as traced by both AGNs and galaxy groups. In the Appendix, we provide spectroscopic redshifts for 49 counterparts to fainter X-ray sources detected only in the 1 and 2 Ms catalogs, and 48 Very Large Array radio sources not detected in X-rays.

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Additional Information:© 2010 American Astronomical Society. Received 2010 April 13; accepted 2010 August 21; published 2010 October 26. Based on observations made with ESO Telescopes at Paranal Observatories under programme IDs 072.A-0139 and 080.A-0411. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation. J.D.S. is supported by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan. The authors recognize support from Michael Cooper for the use of the DEEP2 pipeline that was developed at UC Berkeley with support from NSF grant AST-0071048. W.N.B., B.L., and Y.X. acknowledge support from the Chandra X-ray Center grant SP8-9003A and NASA ADP grant NNX10AC99G. G.S. acknowledges support of the Polányi Fellowship of NKTH. D.A. is funded by the Royal Society and Leverhulme Trust. M.S. and G.H. acknowledge support by the Leibniz Prize of the Deutsche Forschungsgemeinschaft, DFG (HA 1850/28-1). A.C. is supported through ASI-INAF grants I/023/05/00 and I/ 088/06. P.T. acknowledges financial contribution from contract ASIINAF I/088/06/0. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. Facilities: VLT:Melipal(VIMOS), Keck:II(DEIMOS), CXO(ACIS-I)
Funding AgencyGrant Number
World Premier International Research Center Initiative (WPI Initiative)UNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan UNSPECIFIED
Chandra X-ray CenterSP8-9003A
Nemzeti Kutatási és Technológiai Hivatal (NKTH) UNSPECIFIED
Leverhulme TrustUNSPECIFIED
Deutsche Forschungsgemeinschaft (DFG)HA 1850/28-1
Agenzia Spaziale Italiana-Istituto Nazionale di Astrofisica (ASI-INAF)I/023/05/00
Agenzia Spaziale Italiana-Istituto Nazionale di Astrofisica (ASI-INAF)I/088/06
Agenzia Spaziale Italiana-Istituto Nazionale di Astrofisica (ASI-INAF)I/088/06/0
Subject Keywords:galaxies: active; galaxies: Seyfert; quasars: general; surveys; X-rays: galaxies
Classification Code:PACS: 98.70.Qy; 95.30.Gv; 98.65.Bv; 98.65.Cw; 95.85.Kr
Record Number:CaltechAUTHORS:20101220-114038976
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Official Citation:J. D. Silverman et al 2010 ApJS 191 124 doi: 10.1088/0067-0049/191/1/124
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:21442
Deposited By: Jason Perez
Deposited On:23 Dec 2010 16:15
Last Modified:06 Jul 2015 20:28

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