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GALCCXONID - Galactic Center Chandra X-Ray Source Near-IR Counterparts

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Overview

This table contains 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 degrees x 0.8 degrees 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. The authors have cross-correlated the X-ray source positions with the 2MASS and SIRIUS near-infrared catalogs, which collectively contain stars with a 10-sigma limiting flux of K_s <= 15.6 mag. In order to distinguish absorbed infrared sources near the Galactic center from those in the foreground, they defined red and blue sources as those which have H - K_s >= 0.9 and < 0.9 mag, respectively. The authors find that 5.8% =/- 1.5% (2 sigma) 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. The authors 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 their catalog, the authors 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 this catalog and will serve spectroscopic surveys to identify infrared counterparts to X-ray sources near the Galactic center.

Catalog Bibcode

2009ApJ...703...30M

References

 Near-Infrared Counterparts to Chandra X-Ray Sources Toward the Galactic
Center. I. Statistics and a Catalog of Candidates
    Mauerhan J.C., Muno M.P., Morris M.R., Bauer F.E., Nishiyama S., Nagata T.
   <Astrophys. J., 703, 30-41 (2009)>
   =2009ApJ...703...41M

Provenance

This table was created by the HEASARC in October 2009 based on the electronic version of Table 3 from the reference paper which was obtained from the Astrophysical Jounal web site.

Parameters

Source_Number
A sequential identification number for each candidate infrared counterpart to a Chandra X-ray source in order of increasing J2000.0 Right Ascension, i.e., the 'IR source number'.

Name
The source designation (expected to be) recommended by the Dictionary of Nomenclature of Celestial Objects, using the prefix of '[MMM2009]' for Mauerhan, Muno, Morris 2009 and the source number.

Muno_Source_Number
A sequential identification number for each Chandra X-ray source in order of increasing J2000.0 Right Ascension, as tabulated in Muno et al. (2009, ApJS, 181, 110, the HEASARC GALCENCXO table), i.e., the 'X-ray source number'. Notice that there can be multiple IR counterpart matches to an X-ray source.

CXO_Name
The standard IAU-recommended designation for a Galactic Center Chandra X-ray source from the Muno et al. (2009) Catalog, using the 'CXOUGC' prefix and the J2000 equatorial coordinates of the X-ray source, e.g., 'CXOUGC Jhhmmss.s-ddmmss'. Although approximately correct, these are not necessarily equivalent to the actual X-ray positions, which are given in Muno et al. (2009, ApJS, 181, 110, the HEASARC GALCENCXO table).

Xray_Error_Radius
The 95% positional uncertainty (error circle) of the X-ray source, sigma_x, in arcseconds.

Xray_Hardness_Class
The hardness class of the X-ray source (hard or soft), based on its hardness ratio HR_0 = (h-s)/(h+s) where h is the flux in the 2.0 - 3.3 keV energy band, and s is the flux in the 0.5 - 2.0 keV band. Soft sources are defined as sources having -1.0 <= HR_0 <-0.175, while hard sources have HR_0 >= -0.175.or are completely extinguished in the 0.5 - 3.3 keV band. Physically, the value of HR_0 corresponds to an absorbing Hydrogen column density of 4 x 1022 atoms cm-2. Further details are given in Section 2.1 of the reference paper.

IR_Color_Class
The color class of the IR match to the X-ray source (red or blue), defined using a simple selection criterion based on infrared color, as discussed in detail in Section 2.2 of the reference paper.

RA
The Right Ascension of the candidate infrared counterpart to the Chandra X-ray source in the selected equinox. This was given in J2000 coordinates to an accuracy of 10-5 degrees in the original table.

Dec
The Declination of the candidate infrared counterpart to the Chandra X-ray source in the selected equinox. This was given in J2000 coordinates to an accuracy of 10-5 degrees in the original table.

LII
The Galactic Longitude of the candidate infrared counterpart to the Chandra X-ray source.

BII
The Galactic Latitude of the candidate infrared counterpart to the Chandra X-ray source.

Offset
The angular separation between the X-ray source and the particular IR match, in arcseconds.

Bck_IR_Surf_Density
The local background surface density of IR sources, rho(K_s), in sources arcsec-2, having K_s values equivalent to, or greater than, the infrared match in question.

Match_Probability
The percent probability for the given IR match being the genuine counterpart to the X-ray source, as calculated using Equations (2) and (3) in the reference paper. Probabilities for ir_color_class = red matches to xray_hardness_class = soft X-ray source were not computed, as discussed in Section 3.2 of the reference paper, and such cases have been assigned match_probability values of -1.0 in this table.

Jmag
The J-band magnitude of the infrared counterpart to the X-ray source.

Jmag_Error
The uncertainty in the J-band magnitude of the infrared counterpart.

Hmag
The H-band magnitude of the infrared counterpart to the X-ray source.

Hmag_Error
The uncertainty in the H-band magnitude of the infrared counterpart.

Kmag
The K_s-band magnitude of the infrared counterpart to the X-ray source.

Kmag_Error
The uncertainty in the K_s-band magnitude of the infrared counterpart.


Contact Person

Questions regarding the GALCCXONID database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 24-May-2012