A Full Year's Chandra Exposure on SDSS Quasars from the Chandra Multiwavelength Project
Abstract
We study the spectral energy distributions and evolution of a large sample of optically selected quasars from the Sloan Digital Sky Survey (SDSS) that were observed in 323 Chandra images analyzed by the Chandra Multiwavelength Project (ChaMP). Our highest-confidence matched sample includes 1135 X-ray detected quasars in the redshift range 0.2<z<5.4, representing some 36Msec of effective exposure. Spectroscopic redshifts are available for about 1/3 of the detected sample; elsewhere, redshifts are estimated photometrically. With 56 z>3 QSOs detected, 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 are obscured (Nh>1E22), but the fraction might reach ~1/3 if most non-detections are absorbed. We confirm a significant correlation between alpha_ox and optical luminosity, but it flattens or disappears for fainter AGN alone. Gamma hardens significantly both towards higher X-ray luminosity, and for relatively X-ray loud quasars. These trends may represent a relative increase in non-thermal X-ray emission, and our findings thereby strengthen analogies between Galactic black hole binaries and AGN.
Keywords
Cite
@article{arxiv.0809.1058,
title = {A Full Year's Chandra Exposure on SDSS Quasars from the Chandra Multiwavelength Project},
author = {Paul J. Green and T. L. Aldcroft and G. T. Richards and W. A. Barkhouse and A. Constantin and D. Haggard and M. Karovska and D. -W. Kim and M. Kim and A. Vikhlinin and A. Mossman and J. D. Silverman and S. F. Anderson and V. Kashyap and B. J. Wilkes and H. Tananbaum},
journal= {arXiv preprint arXiv:0809.1058},
year = {2008}
}
Comments
28 pages, 21 figures. Accepted (26 Aug 2008) for publication in ApJS. Electronic datafiles (for tables 2 and 3) and high resolution figures available at http://hea-www.harvard.edu/CHAMP/