paper

The Fifth Data Release Sloan Digital Sky Survey/XMM-Newton Quasar Survey

arXiv:0905.0496 · doi:10.1088/0067-0049/183/1/17

Abstract

We present a catalog of 792 DR5 SDSS quasars with optical spectra that have been observed serendipitously in the X-rays with the \emph{XMM-Newton}. These quasars cover a redshift range of z = 0.11 - 5.41 and a magnitude range of i = 15.3-20.7. Substantial numbers of radio-loud (70) and broad absorption line (51) quasars exist within this sample. Significant X-ray detections at >2sigma account for 87% of the sample (685 quasars), and 473 quasars are detected at >6sigma, sufficient to allow X-ray spectral fits. For detected sources, ~ 60% have X-ray fluxes between F(2-10 keV) = 1 - 10 x 10^-14 ergs cm^-2 s^-1. We fit a single power-law, a fixed power-law with intrinsic absorption left free to vary, and an absorbed power-law model to all quasars with X-ray S/N > 6, resulting in a weighted mean photon index Gamma = 1.91 +/- 0.08, with an intrinsic dispersion sigma_Gamma = 0.38. For the 55 sources (11.6%) that prefer intrinsic absorption, we find a weighted mean N_H = 1.5 +/- 0.3 x 10^21 cm^-2. We find that Gamma correlates significantly with optical color, Delta(g-i), the optical-to-X-ray spectral index (alpha_ox) and the X-ray luminosity. While the first two correlations can be explained as artefacts of undetected intrinsic absorption, the correlation between Gamma and X-ray luminosity appears to be a real physical correlation, indicating a pivot in the X-ray slope.

41 pages (preprint style), 11 figures. Published in ApJS, 183, 17. Minor changes to Tables 1 and 2 have been made in the included erratum. Our results remain unchanged

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