Scott F. Anderson et al. 2003 The Astronomical Journal 126 2209 doi:10.1086/378999
Scott F. Anderson1, Wolfgang Voges2, Bruce Margon3, Joachim Trümper2, Marcel A. Agüeros1, Thomas Boller2, Matthew J. Collinge4, L. Homer1, Gregory Stinson1, Michael A. Strauss4, James Annis5, Percy Gómez6, Patrick B. Hall4,7, Robert C. Nichol6, Gordon T. Richards4, Donald P. Schneider8, Daniel E. Vanden Berk9, Xiaohui Fan10, Željko Ivezić4, Jeffrey A. Munn11, Heidi Jo Newberg12, Michael W. Richmond13, David H. Weinberg14, Brian Yanny5, Neta A. Bahcall4, J. Brinkmann15, Masataka Fukugita16 and Donald G. York17
Show affiliationsMany open questions in X-ray astronomy are limited by the relatively small number of objects in uniform optically identified and observed samples, especially when rare subclasses are considered or when subsets are isolated to search for evolution or correlations between wavebands. We describe the initial results of a new program aimed to ultimately yield ~104 fully characterized X-ray source identifications—a sample about an order of magnitude larger than earlier efforts. The technique is detailed and employs X-ray data from the ROSAT All-Sky Survey (RASS) and optical imaging and spectroscopic follow-up from the Sloan Digital Sky Survey (SDSS); these two surveys prove to be serendipitously very well matched in sensitivity. As part of the SDSS software pipelines, optical objects in the SDSS photometric catalogs are automatically positionally cross-correlated with RASS X-ray sources. Then priorities for follow-on SDSS optical spectra of candidate counterparts are automatically assigned using an algorithm based on the known ratios of fx/fopt for various classes of X-ray emitters at typical RASS fluxes of ~10-13 ergs cm-2 s-1. SDSS photometric parameters for optical morphology, magnitude, and colors, plus FIRST radio information, serve as proxies for object class. Initial application of this approach to RASS/SDSS data from 1400 deg2 of sky provides a catalog of more than 1200 spectroscopically confirmed quasars and other AGNs that are probable RASS identifications. Most of these are new identifications, and only a few percent of the AGN counterparts are likely to be random superpositions. The magnitude and redshift ranges of the counterparts are very broad, extending over 15 < m < 21 and 0.03 < z < 3.6, respectively. Although most identifications are quasars and Seyfert 1 galaxies, a variety of other AGN subclasses are also sampled. Substantial numbers of rare AGN types are found, including more than 130 narrow-line Seyfert 1 galaxies and 45 BL Lac candidates. These early results already provide a very sizable set of source identifications, demonstrate the utility of the sample in multiwaveband investigations, and show the capability of the joint RASS/SDSS approach to efficiently proceed toward the largest homogeneously selected/observed sample of X-ray–emitting quasars and other kinds of AGNs.
Issue 5 (2003 November)
Received 2003 May 5, accepted for publication 2003 August 12
Scott F. Anderson et al. 2003 The Astronomical Journal 126 2209
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Y-M Yu et al 2004 J. Phys.: Condens. Matter 16 S5729
A. A. Cowley et al 2009 EPL 85 22001
V. Magnanimo et al 2008 EPL 81 34006
O Panferov et al 2009 Environ. Res. Lett. 4 045019
C Hauptmann and P A Tass 2009 J. Neural Eng. 6 016004
Mukremin Kilic et al. 2009 ApJ 705 1219
C. R. O'Dell et al. 2007 The Astronomical Journal 133 2343
A. J. Westphal and J. P. Bradley 2004 ApJ 617 1131