J/ApJ/721/1663 Near-IR matches of X-ray sources in Gal. Center (DeWitt+, 2010)
Near-infrared counterparts of Chandra X-ray sources toward the Galactic Center.
DeWitt C., Bandyopadhyay R.M., Eikenberry S.S., Blum R., Olsen K.,
Sellgren K., Sarajedini A.
<Astrophys. J., 721, 1663-1679 (2010)>
=2010ApJ...721.1663D 2010ApJ...721.1663D
ADC_Keywords: X-ray sources ; Photometry, infrared ; Milky Way
Keywords: Galaxy: center - infrared: stars - X-rays: stars
Abstract:
The Chandra X-ray Observatory has now discovered nearly 10000 X-ray
point sources in the 2°x0.8° region around the Galactic
Center. The sources are likely to be a population of accreting
binaries in the Galactic Center, but little else is known of their
nature. We obtained JHKs imaging of the 17'x17' region around Sgr A*,
an area containing 4339 of these X-ray sources, with the ISPI camera
on the Cerro Tololo Inter-American Observatory (CTIO) 4m telescope. We
cross-correlate the Chandra and ISPI catalogs to find potential IR
counterparts to the X-ray sources. The extreme IR source crowding in
the field means that it is not possible to establish the authenticity
of the matches with astrometry and photometry alone. We find 2137
IR/X-ray astrometrically matched sources: statistically, we estimate
that our catalog contains 289±13 true matches to soft X-ray sources
and 154±39 matches to hard X-ray sources. However, the fraction of
true counterparts to candidate counterparts for hard sources is just
11%, compared to 60% for soft sources, making hard source NIR matches
particularly challenging for spectroscopic follow-up. We calculate a
color-magnitude diagram (CMD) for the matches to hard X-ray sources,
and find regions where significant numbers of the IR matches are real.
We use their CMD positions to place limits on the absolute Ks-band
magnitudes of the potential NIR counterparts to hard X-ray sources. We
find regions of the counterpart CMD with 9±3 likely
Wolf-Rayet/supergiant binaries (with four spectroscopically confirmed
in the literature) as well as 44±13 candidates that could consist of
either main-sequence high mass X-ray binaries or red giants with an
accreting compact companion. In order to aid spectroscopic follow-up,
we sort the candidate counterpart catalog on the basis of IR and X-ray
properties to determine which source characteristics increase the
probability of a true match. We find a set of 98 IR matches to hard
X-ray sources with reddenings consistent with GC distances which have
a 45% probability of being true counterparts.
Description:
Muno et al. (2009ApJS..181..110M 2009ApJS..181..110M) compile 88 Chandra observations of
the GC taken between 2000 April and 2007 August and find 9017 point
sources over a 2°x0.8° field. The 17'x17' field centered on
Sgr A* has been the target of 1Ms of exposures and has some of the
best sensitivity (4x1031erg/s for GC sources at 8kpc distance) and
the best positional accuracy in the X-ray catalog. Seventy six percent
of the X-ray sources in this region have positional accuracies of
0.7" and better.
We used the ISPI camera on the CTIO 4m Blanco Telescope to observe the
17'x17' central region of the GC, covering the region of highest
source density and in sensitivity in the Chandra X-ray data; with the
J, H, and Ks filters, on 2005 August 10.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 105 2137 *ISPI/Chandra matched sources catalog
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Note on catalog.dat: This table lists the 2137 near-infrared counterparts to
1843 Chandra X-ray sources within the inner 17'x17' of the Galactic Center.
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2012)
II/314 : UKIDSS-DR8 LAS, GCS and DXS Surveys (Lawrence+ 2012)
II/316 : UKIDSS-DR6 Galactic Plane Survey (Lucas+ 2012)
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/MNRAS/417/114 : HST/NICMOS Galactic Center survey catalogue (Dong+, 2011)
J/A+A/511/A18 : NIR observations of stars near SgrA* (Schoedel+, 2010)
J/A+A/499/483 : NIR observations of sources in the GC (Buchholz+, 2009)
J/ApJ/706/223 : X-ray point sources near the Galactic Center (Hong+, 2009)
J/ApJ/703/1323 : Spectroscopy in the Galaxy's nuclear cluster (Do+ 2009)
J/ApJ/703/30 : NIR counterparts to Chandra X-ray sources. I. (Mauerhan+,
2009)
J/ApJ/685/958 : Spitzer and Chandra sources in galactic center (Arendt+ 2008)
J/ApJS/165/173 : Chandra sources in Galaxy central 150pc (Muno+, 2006)
J/ApJ/613/1179 : X-ray sources in Galactic Center (Muno+, 2004)
J/ApJ/589/225 : Chandra X-ray sources toward the GC (Feigelson+, 2003)
http://galcent.astro.ufl.edu/ : Chandra Galactic Survey query page
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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2- 16 A15 --- CXOGC X-ray designation (HHMMSS.s+DDMMSS; J2000) (1)
18- 26 F9.5 deg RAdeg X-ray right ascension (J2000) (1)
28- 36 F9.5 deg DEdeg X-ray declination (J2000) (1)
38- 40 F3.1 arcsec e_pos [0.3/2] X-ray position uncertainty (1)
42- 45 A4 --- XType [Hard/Soft] X-ray source type (Hard or Soft)
47- 57 F11.7 deg RAIdeg ISPI right ascension (J2000)
59- 69 F11.7 deg DEIdeg ISPI declination (J2000)
71- 75 F5.2 mag Jmag [8.56/19.5]?=0 Blanco/ISPI J-band magnitude
78- 81 F4.2 mag e_Jmag ?=0 Jmag uncertainty
83- 87 F5.2 mag Hmag [8.53/19.74]?=0 Blanco/ISPI H-band magnitude
90- 93 F4.2 mag e_Hmag [0.03/0.76]?=0 Hmag uncertainty
95- 99 F5.2 mag Ksmag [8.06/17.94]?=0 Blanco/ISPI Ks-band magnitude
102-105 F4.2 mag e_Ksmag ?=0 Ksmag uncertainty
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Note (1): The X-ray source names, positions and positional uncertainties are
taken from the catalog of Muno et al. (2009ApJS..181..110M 2009ApJS..181..110M).
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Acknowledgements:
Curtis DeWitt (University of Florida) - Chandra Galactica catalog
(End) Curtis DeWitt [UFL], Emmanuelle Perret [CDS] 06-Feb-2013