Chandra Observations of 12 Luminous Red Quasars

We present results of a study of 12 dust-reddened quasars with 0.4 < z < 2.65 and reddenings in the range 0.15 < E(B − V ) < 1.7. We obtained ACIS-S X-ray spectra of these quasars, estimated the column densities towards them, and hence obtained the gas:dust ratios in the material obscuring the quasar. We detect all but one of the red quasars in the X-rays. Even though there is no obvious correlation between the X-ray determined column densities of our sources and their optical color or reddening, all of the sources show absorbed X-ray spectra. When we correct the luminosity for absorption, they can be placed among luminous quasars; therefore our objects belong to the group of high luminosity analogues of the sources contributing to the X-ray background seen in deep X-ray observations. Such sources are also found in serendipitous shallow X-ray surveys. There is a hint that the mean spectral slope of the red quasar is higher than that of normal, unobscured quasars, which could be an indication for higher accretion rates and/or an evolutionary effect. We investigate the number density of these sources compared to type 2 AGN based on the X-ray background and estimate how many moderate luminosity red quasars may be found in deep X-ray fields. Subject headings: Quasars: X-rays, absorption, dust — galaxies: EROs Department of Physics, University of California, One Shields Avenue, Davis, CA 95616; [email protected] IGPP, L-413, Lawrence Livermore National Laboratory, Livermore, CA 94550; [email protected], [email protected] Spitzer Science Center, MS 314-6, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125; [email protected]