Astrophys. J., 690, 644-669 (2009/January-1)
A full year's Chandra exposure on Sloan Digital Sky Survey quasars from the Chandra multiwavelength project.
GREEN P.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. and TANANBAUM H.
Abstract (from CDS):
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 Γ or for the ratio of optical/UV to X-ray flux αox. About 10% of detected QSOs show best-fit intrinsic absorbing columns greater than 1022/cm2, but the fraction might reach ∼1/3 if most nondetections are absorbed. We confirm a significant correlation between αox and optical luminosity, but it flattens or disappears for fainter (MB≳ -23) active galactic nucleus (AGN) alone. We report significant hardening of Γ 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 αox or Γ.
galaxies: active - quasars: absorption lines - quasars: general - surveys - X-rays: general
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<Available at CDS (J/ApJ/690/644): table2.dat table3.dat>
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