Astronomy and Astrophysics – Astrophysics
Scientific paper
2006-06-16
Astron.J.132:1977-1988,2006
Astronomy and Astrophysics
Astrophysics
20 pages emulateapj5 style, 7 figures, 4 tables. submitted to AJ
Scientific paper
10.1086/507842
We present short \chandra observations of twelve bright (i<18) z_em~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~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 AGN (as opposed to fully obscured type 2 AGN) 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 broad-band colors.
Alexander Dave M.
Anderson Scott F.
Bauer Florian
Brandt Wiliam N.
Gallagher Sarah C.
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