J/PASJ/74/283 NIR identified X-ray sources in Galactic bulge (Morihana+, 2022)
Deep near-infrared imaging observation of the faint X-ray point sources
constituting the Galactic bulge X-ray emission.
Morihana K., Tsujimoto M., Ebisawa K., Gandhi P.
<Publ. Astron. Soc. Jap., 74, 283-297 (2022)>
=2022PASJ...74..283M 2022PASJ...74..283M (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way ; X-ray sources ; Infrared sources
Keywords: Galaxy: stellar content - novae, cataclysmic variables -
stars: late-type - X-rays: diffuse background - X-rays: stars
Abstract:
The presence of the apparently extended hard (2-10keV) X-ray emission
along the Galactic plane has been known since the early 1980s. With a
deep X-ray exposure using the Chandra X-ray Observatory of a slightly
off-plane region in the Galactic bulge, most of the extended emission
was resolved into faint discrete X-ray sources in the Fe K band
(Revnivtsev et al., 2009Natur.458.1142R 2009Natur.458.1142R). The major constituents of
these sources have long been considered to be X-ray active stars and
magnetic cataclysmic variables (CVs). However, recent works including
our near-infrared (NIR) imaging and spectroscopic studies (Morihana et
al., 2013ApJ...766...14M 2013ApJ...766...14M, Cat. J/ApJ/766/14; Morihana et al.,
2016PASJ...68...57M 2016PASJ...68...57M) argue that other populations should be more
dominant. To investigate this further, we conducted a much deeper NIR
imaging observation at the center of the Chandra's exposure field. We
have used the MOIRCS on the Subaru telescope, reaching the limiting
magnitude of ∼18mag in the J, H, and Ks bands in this crowded
region, and identified ∼50% of the X-ray sources with NIR candidate
counterparts. We classified the X-ray sources into three groups (A, B,
and C) based on their positions in the X-ray color-color diagram and
characterized them based on the X-ray and NIR features. We argue that
the major populations of the Group A and C sources are, respectively,
CVs (binaries containing magnetic or non-magnetic white dwarfs with
high accretion rates) and X-ray active stars. The major population of
the Group B sources is presumably white dwarf (WD) binaries with low
mass accretion rates. The Fe K equivalent width in the composite X-ray
spectrum of the Group B sources is the largest among the three and
comparable to that of the Galactic bulge X-ray emission. This leads us
to speculate that there are numerous WD binaries with low mass
accretion rates which are not recognized as CVs but are the major
contributor of the apparently extended X-ray emission.
Description:
A deep JHKs imaging observation of the Chandra bulge field (CBF) was
carried out using MOIRCS on the Subaru telescope. MOIRCS is equipped
with two 2048x2048 HgCdTe HAWAII-2 arrays and covers a 4x7-arcmin2
field of view with a pixel scale of 0.117"/pixel in the imaging mode.
We look for candidate NIR counterparts to the Chandra X-ray sources.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 117 264 NIR identified X-ray source catalog
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See also:
J/ApJ/766/14 : Deep Chandra bulge field X-ray point sources (Morihana+, 2013)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 4 I4 --- Seq X-ray catalog source number in Morihana et
al. (2013ApJ...766...14M 2013ApJ...766...14M, Cat. J/ApJ/766/14)
6- 23 A18 --- CXOU CXOU J designation (HHMMSS.ss+DDMMSS.s)
25- 34 F10.6 deg RAdeg X-ray right ascension (J2000)
36- 44 F9.5 deg DEdeg X-ray declination (J2000)
46- 54 F9.5 deg RANdeg NIR right ascension (J2000)
56- 64 F9.5 deg DENdeg NIR declination (J2000)
66- 68 F3.1 arcsec ePos X-ray position error (1σ)
70- 76 E7.2 mW/m2 F0.5-8keV Photometric flux in the total (0.5-8.0keV)
band (1)
78- 84 E7.2 mW/m2 F2-8keV ?=- Photometric flux in the hard (2.0-8.0keV)
band (1)
86- 90 F5.2 mag Jmag ?=0 Subaru J magnitude
92- 95 F4.2 mag e_Jmag ?=0 Subaru J magnitude error
97-101 F5.2 mag Hmag ?=0 Subaru H magnitude
103-106 F4.2 mag e_Hmag ?=0 Subaru H magnitude error
108-112 F5.2 mag Ksmag ?=0 Subaru Ks magnitude
114-117 F4.2 mag e_Ksmag ?=0 Subaru Ks magnitude error
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Note (1): The photometric flux is defined as count rate multiplied by the
median energy divided by the average effective area (Tsujimoto et al.,
2005AJ....130.2212T 2005AJ....130.2212T, Cat. J/AJ/130/2212, Morihana et al., 2013ApJ...766...14M 2013ApJ...766...14M,
Cat. J/ApJ/766/14)
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 21-Sep-2022