AAS 205th Meeting, 9-13 January 2005
Session 143 Quasars
Poster, Thursday, January 13, 2005, 9:20am-4:00pm, Exhibit Hall

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[143.15] Shedding Light on the Dust in Obscured Quasars

E. Glikman, D. J. Helfand (Columbia University), R. H. Becker (UC Davis), R. L. White (STScI), M. D. Gregg (UC Davis), M. Lacy (Spitzer Science Center)

Recent studies have begun to reveal the presence of a red population of quasars which have been long-sought in order to explain the x-ray background, as well as to illuminate models of quasar evolution and their connection to the evolution of galaxies. Using the FIRST and 2MASS surveys we have identified over 100 heavily reddened quasars (0.1 < E(B-V) < 1.5) by selecting objects with optical-near-infrared colors such that R-K>4 and J-K>1.7; 50 percent of such objects with 20cm flux densities greater than 1 mJy are red quasars. Their colors may arise from dust extinction and/or a red synchrotron component associated with a flat radio spectrum. We have obtained contemporaneous 20cm and 3cm measurements of about 50 of these quasars to determine the extent to which red synchrotron emission contributes; in most cases, dust obscuration is required. We also present an optical to near-infrared quasar composite spectrum spanning 0.1-4 microns constructed from observations of low redshift (z<0.38), normal, blue SDSS-selected quasars. This spectrum is useful, among other things, for exploring quantitatively the extinction in our red quasars.

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