THE SWIRE/CHANDRA SURVEY: THE X-RAY SOURCES
- Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)
- Department of Astronomy, Wesleyan University, CT 06459 (United States)
- Korea Astronomy and Space Science Institute (KASI), 61-1, Hwaam-dong, Yuseong-gu, Deajeon 305-348 (Korea, Republic of)
- INAF-ISAF Milano, via E. Bassini 15, Milano 20133 (Italy)
- The National Radio Astronomy Observatory, Charlottesville, VI 22902 (United States)
- Center for Astrophysics and Space Science, University of California, San Diego, La Jolla, CA 92093-0424 (United States)
- Spitzer Science Center, California Institute of Technology, 100-22, Pasadena, CA 91125 (United States)
- National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 (United States)
- Dipartimento Di Astronomia, Universita di Padova, Vicolo Osservatorio 5, I-35122 Padua (Italy)
- California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States)
We report a moderate-depth (70 ks), contiguous 0.7 deg{sup 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 {sub H} > 23) subset. Chandra has detected 775 X-ray sources to a limiting broadband (0.3-8 keV) flux {approx}4 x 10{sup -16} erg cm{sup -2} s{sup -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 {mu}m detections. There are four optical-only X-ray sources and four with no visible optical/IR counterpart. The very deep ({approx}2.7 {mu}Jy rms) VLA data yield 251 (>4{sigma}) 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{sub r} /f{sub 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{sub L} . The majority of these are red and relatively faint in the optical so that the use of R{sub L} to select those AGNs with the strongest radio emission becomes questionable. Using the 24 {mu}m to radio flux ratio (q {sub 24}) instead results in 13 of the 147 AGNs with sufficient data being classified as radio-loud, in good agreement with the {approx}10% expected for broad-lined AGNs based on optical surveys. We conclude that q {sub 24} is a more reliable indicator of radio-loudness. Use of R{sub L} should be confined to the optically selected type 1 AGN.
- OSTI ID:
- 21301478
- Journal Information:
- Astrophysical Journal, Supplement Series, Vol. 185, Issue 2; Other Information: DOI: 10.1088/0067-0049/185/2/433; Country of input: International Atomic Energy Agency (IAEA); ISSN 0067-0049
- Country of Publication:
- United States
- Language:
- English
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