2008ApJ...688..128Y

We have cross-correlated the SDSS DR3 Schneider et al. ((ref???)2005) quasar catalog with the XMM-Newton archive. Color and redshift selections (g-r≥0.5 and 0.9<z<2.1) result in a sample of 17 red, moderate-redshift quasars. The redshift selection minimizes possible contamination due to host galaxy emission and Lyα forest absorption. Both optical and X-ray information is required to distinguish between the two likely remaining causes of the red colors: (1) dust reddening and (2) an intrinsically red continuum. We find that 7 of 17 quasars can be classified as probable ``intrinsically red'' objects. These seven quasars have unusually broad Mg II emission lines (<FWHM≥10,500 km/s), moderately flat but unabsorbed X-ray spectra (<Γ≥1.66±0.08), and low accretion rates (M{dot}/M{dot}_Edd∼0.01). We suggest low accretion rates as a possible physical explanation for quasars with intrinsically red optical continua. We find that 8 of 17 quasars can be classified as dust reddened. Three of these have upper limits on the absorption column from X-ray spectral fits of N_H=(3-13)x10²² cm2, while the other five quasars must be absorbed by at least N_H=10²³ cm2 in order to be consistent with a comparably selected α_ox-l_uvdistribution. Two objects in the sample are unclassified.