2004AJ....127.2579Z -
Astron. J., 127, 2579-2597 (2004/May-0)
Multicolor photometric observations of candidate optical counterparts to ROSAT faint X-ray sources in a 1 square degree field of the BATC survey.
ZHANG H., XUE S., BURSTEIN D., ZHOU X., JIANG Z., WU H., MA J., CHEN J. and ZOU Z.
Abstract (from CDS):
We present optical candidates for 75 X-ray sources in a ∼1 deg2 overlapping region with the 1997 medium-deep ROSAT survey by Molthagen et al. These candidates are selected using the multicolor CCD imaging observations made for the T329 field of the Beijing-Arizona-Taiwan-Connecticut (BATC) Sky Survey, which uses the NAOC 0.6/0.9 m Schmidt telescope with 15 intermediate-band filters covering the wavelength range 3360-9745 Å. These X-ray sources are relatively faint (CR≪0.2/s) and thus are mostly not included in the ROSAT Bright Source Catalogue; they also remain as X-ray sources without optical candidates in a previous identification program carried out by the Hamburg Quasar Survey. Within their position error circles, almost all of the X-ray sources are observed to contain one or more spatially associated optical candidates down to the magnitude mV∼23.1. We have classified 149 of 156 detected optical candidates with 73 of the 75 X-ray sources with a new method that predicts a redshift for nonstellar objects, which we have termed the SED-based Object Classification Approach. These optical candidates include 31 QSOs, 39 stars, 37 starburst galaxies, 42 galaxies, and seven ``just''-visible objects. Twenty-eight X-ray error circles have only one visible object in them: nine QSOs, three normal galaxies, eight starburst galaxies, six stars, and two of the just-visible objects. We have also cross-correlated the positions of these optical objects with NASA Extragalactic Database, the FIRST radio source catalog, and the Two Micron All Sky Survey. Separately, we have also SED-classified the remaining 6011 objects in our field of view. Optical objects are found at the 6.5 σ level above what one would expect from a random distribution; only QSOs are overrepresented in these error circles at greater than 4 σ frequency. We estimate redshifts for all extragalactic objects and find a good correspondence between our predicted redshift and the measured redshift (a mean error of 0.04 in Δz). There appears to be a supercluster at z∼0.3-0.35 in this direction, including many of the galaxies in the X-ray error circles that are found in this redshift range.
Abstract Copyright:
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Journal keyword(s):
Catalogs - Galaxies: Active - Surveys - X-Rays
VizieR on-line data:
<Available at CDS (J/AJ/127/2579): table2.dat>
Nomenclature:
Table 2: [ZXB2004] RX JHHMM.m+DDMM N=75.
Simbad objects:
80
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