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The SWIRE/Chandra Survey: The X-ray Sources

Wilkes, Belinda J. and Kilgard, Roy and Kim, Dong-Woo and Kim, Minsun and Polletta, M. and Lonsdale, Carol and Smith, Harding E. and Surace, Jason and Owen, Frazer N. and Franceschini, A. and Siana, Brian and Shupe, D. (2009) The SWIRE/Chandra Survey: The X-ray Sources. Astrophysical Journal Supplement Series, 185 (2). pp. 433-450. ISSN 0067-0049.

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We report a moderate-depth (70 ks), contiguous 0.7 deg^2 Chandra survey in the Lockman Hole Field of the Spitzer/SWIRE Legacy Survey coincident with a completed, ultra-deep VLA survey with deep optical and near-infrared imaging in-hand. The primary motivation is to distinguish starburst galaxies and active galactic nuclei (AGNs), including the significant, highly obscured (log N_H > 23) subset. Chandra has detected 775 X-ray sources to a limiting broadband (0.3-8 keV) flux ~4 × 10^(–16) erg cm^(–2) s^(–1). We present the X-ray catalog, fluxes, hardness ratios, and multi-wavelength fluxes. The log N versus log S agrees with those of previous surveys covering similar flux ranges. The Chandra and Spitzer flux limits are well matched: 771 (99%) of the X-ray sources have infrared (IR) or optical counterparts, and 333 have MIPS 24 μm detections. There are four optical-only X-ray sources and four with no visible optical/IR counterpart. The very deep (~2.7 μJy rms) VLA data yield 251 (>4σ) radio counterparts, 44% of the X-ray sources in the field. We confirm that the tendency for lower X-ray flux sources to be harder is primarily due to absorption. As expected, there is no correlation between observed IR and X-ray fluxes. Optically bright, type 1, and red AGNs lie in distinct regions of the IR versus X-ray flux plots, demonstrating the wide range of spectral energy distributions in this sample and providing the potential for classification/source selection. Many optically bright sources, which lie outside the AGN region in the optical versus X-ray plots (f_r /f_x >10), lie inside the region predicted for red AGNs in IR versus X-ray plots, consistent with the presence of an active nucleus. More than 40% of the X-ray sources in the VLA field are radio-loud using the classical definition, R_L . The majority of these are red and relatively faint in the optical so that the use of R_L to select those AGNs with the strongest radio emission becomes questionable. Using the 24 μm to radio flux ratio (q_(24)) instead results in 13 of the 147 AGNs with sufficient data being classified as radio-loud, in good agreement with the ~10% expected for broad-lined AGNs based on optical surveys. We conclude that q_(24) is a more reliable indicator of radio-loudness. Use of R_L should be confined to the optically selected type 1 AGN.

Item Type:Article
Related URLs:
URLURL TypeDescription
Wilkes, Belinda J.0000-0003-1809-2364
Polletta, M.0000-0001-7411-5386
Lonsdale, Carol0000-0003-0898-406X
Surace, Jason0000-0001-7291-0087
Siana, Brian0000-0002-4935-9511
Shupe, D.0000-0003-4401-0430
Additional Information:© 2009 American Astronomical Society. Print publication: Issue 2 (2009 December); received 2009 February 18; accepted for publication 2009 October 21; published 2009 November 17. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.We gratefully acknowledge the financial support of NASA Contract: NAS8-03060 (Chandra X-ray Center, B.W.) and ChandraGOgrant: GO4-5158A (R.K.).M.P. acknowledges financial contribution from contractsASI-INAF I/016/07/0 and ASI-INAF I/088/06/0.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Agenzia Spaziale Italiana (ASI)ASI-INAF I/016/07/0
Agenzia Spaziale Italiana (ASI)ASI-INAF I/088/06/0
Istituto Nazionale di Astrofisica (INAF)UNSPECIFIED
Subject Keywords:catalogs; quasars: general; surveys; X-rays: galaxies
Issue or Number:2
Record Number:CaltechAUTHORS:20100104-122034465
Persistent URL:
Official Citation:The SWIRE/Chandra Survey: The X-ray Sources Belinda J. Wilkes, Roy Kilgard, Dong-Woo Kim, Minsun Kim, Mari Polletta, Carol Lonsdale, Harding E. Smith, Jason Surace, Frazer N. Owen, A. Franceschini, Brian Siana, and David Shupe 2009 ApJS 185 433-450 doi: 10.1088/0067-0049/185/2/433
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:17049
Deposited By: Jason Perez
Deposited On:07 Jan 2010 00:25
Last Modified:30 Sep 2020 17:57

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