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Date and Time of the Query: 2018-12-16 T09:13:31 PST
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For refcode 2009ApJ...690..644G:
Retrieve 1135 NED objects in this reference.
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Copyright by American Astronomical Society. Reproduced by permission
2009ApJ...690..644G A Full Year's Chandra Exposure on Sloan Digital Sky Survey Quasars from the Chandra Multiwavelength Project Green, Paul J.; Aldcroft, T. L.; Richards, G. T.; Barkhouse, W. A.; Constantin, A.; Haggard, D.; Karovska, M.; Kim, D.-W.; Kim, M.; Vikhlinin, A.; Anderson, S. F.; Mossman, A.; Kashyap, V.; Myers, A. C.; Silverman, J. D.; Wilkes, B. J.; Tananbaum, H. Abstract. We study the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project. Our highest-confidence matched sample includes 1135 X-ray detected quasars in the redshift range 0.2 < z < 5.4, representing some 36 Msec of effective exposure. We provide catalogs of QSO properties, and describe our novel method of calculating X-ray flux upper limits and effective sky coverage. Spectroscopic redshifts are available for about 1/3 of the detected sample; elsewhere, redshifts are estimated photometrically. We detect 56 QSOs with redshift z > 3, substantially expanding the known sample. We find no evidence for evolution out to z ~ 5 for either the X-ray photon index {GAMMA} or for the ratio of optical/UV to X-ray flux {alpha}_ox_. About 10% of detected QSOs show best-fit intrinsic absorbing columns greater than 10^22^ cm^-2^, but the fraction might reach ~1/3 if most nondetections are absorbed. We confirm a significant correlation between {alpha}_ox_ and optical luminosity, but it flattens or disappears for fainter (M_B_ >~ -23) active galactic nucleus (AGN) alone. We report significant hardening of {GAMMA} both toward higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in nonthermal X-ray emission, and our findings thereby strengthen analogies between Galactic black hole binaries and AGN. For uniformly selected subsamples of narrow-line Seyfert 1s and narrow absorption line QSOs, we find no evidence for unusual distributions of either {alpha}_ox_ or {GAMMA}. Key words: galaxies: active, quasars: absorption lines, quasars: general, surveys, X-rays: general
Retrieve 1135 NED objects in this reference.
Please click here for ADS abstract

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