A Caltech Library Service

Near-Infrared Counterparts to Chandra X-Ray Sources Toward the Galactic Center. I. Statistics and a Catalog of Candidates

Mauerhan, J. C. and Muno, M. P. and Morris, M. R. and Bauer, F. E. and Nishiyama, S. and Nagata, T. (2009) Near-Infrared Counterparts to Chandra X-Ray Sources Toward the Galactic Center. I. Statistics and a Catalog of Candidates. Astrophysical Journal, 703 (1). pp. 30-41. ISSN 0004-637X.

PDF - Published Version
See Usage Policy.


Use this Persistent URL to link to this item:


We present a catalog of 5184 candidate infrared counterparts to X-ray sources detected toward the Galactic center. The X-ray sample contains 9017 point sources detected in this region by the Chandra X-ray Observatory during the past decade, including data from a recent deep survey of the central 2° × 0°.8 of the Galactic plane. A total of 6760 of these sources have hard X-ray colors, and the majority of them lie near the Galactic center, while most of the remaining 2257 soft X-ray sources lie in the foreground. We cross-correlated the X-ray source positions with the 2MASS and SIRIUS near-infrared catalogs, which collectively contain stars with a 10σ limiting flux of K_s ≤ 15.6 mag. In order to distinguish absorbed infrared sources near the Galactic center from those in the foreground, we defined red and blue sources as those which have H – K_s ≥ 0.9 and <0.9 mag, respectively. We find that 5.8% ± 1.5% (2σ) of the hard X-ray sources have real infrared counterparts, of which 228 ± 99 are red and 166 ± 27 are blue. The red counterparts are probably comprised of Wolf-Rayet and O stars, high-mass X-ray binaries, and symbiotic binaries located near the Galactic center. Foreground X-ray binaries suffering intrinsic X-ray absorption could be included in the sample of blue infrared counterparts to hard X-ray sources. We also find that 39.4% ± 1.0% of the soft X-ray sources have blue infrared counterparts; most of these are probably coronally active dwarfs in the foreground. There is a noteworthy collection of ≈20 red counterparts to hard X-ray sources near the Sagittarius B H II region, which are probably massive binaries that have formed within the last several Myr. For each of the infrared matches to X-ray sources in our catalog we derived the probability that the association is real, based on the source properties and the results of the cross-correlation analysis. These data are included in our catalog and will serve spectroscopic surveys to identify infrared counterparts to X-ray sources near the Galactic center.

Item Type:Article
Related URLs:
URLURL TypeDescription
Morris, M. R.0000-0002-6753-2066
Bauer, F. E.0000-0002-8686-8737
Additional Information:© 2009 American Astronomical Society. Print publication: Issue 1 (2009 September 20); received 2009 January 7; accepted for publication 2009 July 21; published 2009 August 25. This research was based upon observations made with the Chandra X-ray Observatory. Support for this research was provided through Chandra award No. GO6-7135I. We thank the referee for a very insightful and helpful critique of this manuscript.
Funding AgencyGrant Number
Subject Keywords:catalogs; Galaxy: center; infrared: stars; surveys; X-rays: binaries; X-rays: stars
Issue or Number:1
Record Number:CaltechAUTHORS:20090929-115628373
Persistent URL:
Official Citation:Near-Infrared Counterparts to Chandra X-Ray Sources Toward the Galactic Center. I. Statistics and a Catalog of Candidates J. C. Mauerhan, M. P. Muno, M. R. Morris, F. E. Bauer, S. Nishiyama, and T. Nagata 2009 ApJ 703 30-41 doi: 10.1088/0004-637X/703/1/30
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:16114
Deposited By: Jason Perez
Deposited On:02 Oct 2009 21:56
Last Modified:04 Nov 2019 21:50

Repository Staff Only: item control page