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C. M. Urry, E. Treister, J. Van Duyne (Yale U.), F. E. Bauer (IoA Cambridge), N. A. Grogin, A. Koekemoer (STScI), D. Stern (JPL/Caltech), GOODS AGN Team Collaboration
The Great Observatories Origins Deep Survey (GOODS) is a multiwavelength study, ranging from hard X-rays to the mid-infrared, designed in part to find obscured AGN in the early Universe, particularly at the ``quasar epoch," at z~2. The unprecedented area and depth of GOODS, with its 4-band HST ACS imaging, megasecond Chandra pointings, and Spitzer IRAC and MIPS observations, provides a unique probe of faint, reddened AGN at high redshift. We show that extending the local ratio of roughly 3 times as many obscured AGN as unobscured to higher redshift fits very well the optical, infrared, and X-ray source counts in the GOODS fields, with essentially no free parameters (once the unification geometry is set). This model also reproduces the spectrum and intensity of the X-ray background. Some reported ``evolution" in the ratio of obscured to unobscured AGN --- for example with luminosity, redshift, or flux --- can be explained easily by selection bias against the fainter obscured AGN. Based on observations obtained with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc, under NASA contract NAS5-26555. This work was supported in part by NASA grant HST-GO-09425.13-A.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.