Chandra observations of red Sloan Digital Sky Survey quasars

被引:20
|
作者
Hall, Patrick B.
Gallagher, S. C.
Richards, Gordon T.
Alexander, D. M.
Anderson, Scott F.
Bauer, Franz
Brandt, W. N.
Schneider, Donald P.
机构
[1] Princeton Univ Observ, Princeton, NJ 08544 USA
[2] York Univ, Dept Phys & Astron, N York, ON M3J 1P3, Canada
[3] Univ Calif Los Angeles, Dept Phys & Astron, Los Angeles, CA 90095 USA
[4] Johns Hopkins Univ, Dept Phys & Astron, Baltimore, MD 21218 USA
[5] Univ Cambridge, Inst Astron, Cambridge CB3 0HA, England
[6] Univ Washington, Dept Astron, Seattle, WA 98195 USA
[7] Columbia Univ, Dept Astron, New York, NY 10027 USA
[8] Penn State Univ, Dept Astron & Astrophys, University Pk, PA 16802 USA
来源
ASTRONOMICAL JOURNAL | 2006年 / 132卷 / 05期
关键词
quasars : absorption lines; quasars : general; X-rays : galaxies;
D O I
10.1086/507842
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present short Chandra observations of 12 bright (i < 18) z(em) similar to 1.5 quasars from the Sloan Digital Sky Survey chosen to have significantly redder optical colors than most quasars at the same redshift. Of the five quasars with optical properties most consistent with dust reddening at the quasar redshift, four show indirect evidence of moderate X-ray absorption (inferred N-H similar to 10(22) cm(-2)) with a dust-to-gas ratio < 1% of the SMC value. The remaining seven objects show no evidence for even moderate intrinsic X-ray absorption. Thus, while optically red quasars are marginally more likely to show signatures of X-ray absorption than optically selected quasars with normal colors, dust-reddened type 1 active galactic nuclei (as opposed to fully obscured type 2 active galactic nuclei) are unlikely to contribute significantly to the remaining unresolved hard X-ray background. The red quasar population includes objects with intrinsically red continua, as well as objects with dust-reddened continua. Improved sample selection is thus needed to increase our understanding of either subpopulation. To identify dust-reddened quasars likely to exhibit X-ray absorption, some measure of spectral curvature is preferable to simple cuts in observed or relative broadband colors.
引用
收藏
页码:1977 / 1988
页数:12
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