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L. M. Perez (Universidad de Chile), M. G. Smith (NOAO), B. J. Wilkes, P. J. Green, A. Mossman, M. Kim (SAO/Center for Astrophysics), B. T. Januzzi (NOAO), W. A. Barkhouse, J. D. Silverman (SAO/Center for Astrophysics), P.S. Smith (Steward Observatory, The University of Arizona), D. Norman (NOAO), D.-W. Kim (SAO/Center for Astrophysics)
The study of the luminosity function of quasars and its evolution over cosmic time has been bedeviled with selection effects. Selection at purely optical wavelengths, for example, overlooks most heavily obscured sources - and will miss objects with redshifts so high that the interstellar medium is still largely neutral and Lyman alpha emission is redshifted out of the optical region of the spectrum. We have found that selection using X-rays yields more quasars per square degree down to a given optical magnitude than any other selection technique employed to date.
We present the preliminary results of a pilot X-ray, infrared and optical search to identify - and begin to study - the nature of the missing population of faint red quasars in 3 ChaMP X-ray fields. Our AGN catalog from these fields was originally selected based on coincidence of hard-X-ray (Chandra) and near-IR point sources. To locate the red quasars, we have further selected a number of candidates with J<22 mag and Ks <20.3 mag for follow-up infrared spectroscopy, using the criteria J-K<1.5 and r'-Ks<4 – similar to the color criteria proposed and used successfully by Glikman et al. Using IR slit spectroscopy, these authors found that ~50% of their (much brighter) candidates, selected in this manner, turn out to be obscured quasars.
Our near-IR photometric observations, (taken with the ISPI camera, which gives a 100-square-arcminute FOV on the 4m Blanco telescope at Cerro Tololo) are believed to be the deepest so far made with this instrument. This set of pilot data will serve as a prototype for more extensive observations being planned with the NEWFIRM camera, which will provide a FOV four times that of ISPI. The next step is to obtain spectroscopy with an 8m-class telescope.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.