AAS 203rd Meeting, January 2004
Session 63 AGN
Oral, Tuesday, January 6, 2004, 10:00-11:30am, Regency VII

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[63.04] The Contribution of Red 2MASS AGN to the Cosmic X-ray Background

B.J. Wilkes (SAO), G. Risaliti (INAF, Firenze), H. Ghosh (OSU), R. Cutri (IPAC), R. Gilli (INAF, Firenze), B. Nelson (IPAC)

The red active galactic nuclei (AGNs) found using the Two Micron All Sky Survey (2MASS) have a surface density that is comparable to that found in earlier UV and optical searches such as the PG and Hamburg surveys. Newer more sensitive optical searches, such as the LBQS, 2dF and SDSS detect more of the red AGN population, but still miss some fraction of them even at low redshift. The 2MASS sample includes broad, intermediate and narrow lined AGN, with the latter in the minority by a factor of 3, and is highly optically polarised. Chandra observations show that the red AGN are generally X-ray faint and have hard spectra suggestive of absorption at the level of log NH 21-23, making them likely contributors to the absorbed AGN population required by models for the Cosmic X-ray Background (CXRB). This would reduce the need for the, so far elusive, but dominant population of type 2 AGN predicted by previous CXRB models. We estimate that the contribution of the 2MASS red AGN to the CXRB may be as high as 30%, with uncertainties depending on their intrinsic spectral energy distributions (SEDs), intrinsic X-ray flux and evolution with redshift.

The financial support of NASA grant GO3-4138A and NASA contract NAS8-39073 (CXC) are gratefully acknowledged.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.