J/ApJ/695/1094 Chandra observations of NGC 4636 (Posson-Brown+, 2009)
Chandra observations of the X-ray point source population in NGC 4636.
Posson-Brown J., Raychaudhury S., Forman W., Donnelly R.H., Jones C.
<Astrophys. J., 695, 1094-1110 (2009)>
=2009ApJ...695.1094P 2009ApJ...695.1094P
ADC_Keywords: Galaxies, nearby ; Binaries, X-ray ; Clusters, globular ;
Photometry
Keywords: galaxies: individual (NGC 4636) - X-rays: binaries - X-rays: galaxies
Abstract:
We present the X-ray point-source population in the nearby Virgo
elliptical galaxy NGC 4636 from three Chandra X-ray observations.
These observations, totaling ∼193ks after time filtering, were taken
with the Advanced CCD Imaging Camera (ACIS) over a three-year period.
Using a wavelet decomposition detection algorithm, we detect 318
individual point sources. For our analysis, we use a subset of 277
detections with ≥net 10 counts (a limiting luminosity of
approximately 1.2x1037erg/s in the 0.5-2keV band, outside the
central 1.5' bright galaxy core). We present a radial distribution of
the point sources. Between 1.5' and 6' from the center, 25% of our
sources are likely to be background sources (active galactic nuclei
(AGNs)) and 75% are low-mass X-ray binaries (LMXBs) within the galaxy,
while at radial distances greater than 6', background sources (AGN)
will dominate the point sources. We find 77 matches between X-ray
point sources and globular cluster (GC) candidates found in deep
optical images of NGC 4636. In the annulus from 1.5' to 6' of the
galaxy center, 48 of the 129 X-ray point sources (37%) with ≥10 net
counts are matched with GC candidates. Since we expect 25% of these
sources to be background AGN, the percentage matched with GCs could be
as high as 50%. Of these matched sources, we find that ∼70% are
associated with the redder GC candidates, those that are thought to
have near-solar metal abundance.
Description:
The observations presented in this paper were made with Chandra on
three occasions spanning three years: with ACIS-I detector in 2003 Feb
14-15 and with ACIS-S in 2000 Jan 26.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 67 277 Summary of X-ray point sources detected in
NGC 4636
table3.dat 58 77 X-ray point sources matched with globular
clusters candidates in NGC 4636
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-)
J/ApJ/602/231 : Chandra X-ray point sources in nearby galaxies (Colbert+,
2004)
J/A+A/433/43 : C-T1 phot. of NGC 4636 globular cluster system (Dirsch+, 2005)
J/A+A/459/391 : Dynamics of NGC 4636 globular cluster system (Schuberth+,
2006)
J/A+A/488/1221 : BMW-Chandra source catalog (Romano+, 2008)
J/ApJS/192/10 : Chandra ACIS survey in 383 nearby galaxies. I. (Liu, 2011)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
10- 15 F6.4 deg DEdeg Declination in decimal degrees (J2000)
17- 19 I3 ct Nct Net 0.5-2keV band counts
21- 29 E9.3 10-7W Lum The 0.5-2keV band luminosity in erg/s
31- 35 F5.2 --- HR1 Soft color (1)
37- 41 F5.2 --- HR2 Hard Color (2)
43- 47 F5.2 arcmin Dist Distance of source from center
49 I1 --- Inst [1/3] Instrument code (3)
51- 61 A11 --- Var Variability code (4)
63- 64 A2 --- --- [GC] if source matches with a globular cluster
66- 67 I2 --- GC ? GC number in table 3
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Note (1): Defined as (M-S)/(S+M+H) where S, M, and H are the fluxes in bands
0.5-1, 1-2, and 2-8keV, respectively.
Note (2): Defined as (H-M)/(S+M+H) where S, M, and H are the fluxes in bands
0.5-1, 1-2, and 2-8keV, respectively.
Note (3): Code as follows:
1 = source was detected by the ACIS-S;
2 = source was detected by the ACIS-I;
3 = source was detected by both instruments;
Note (4): Abbreviation in note as follows:
V = a long-term (i.e. between observations) variable;
SV = a short-term (i.e. during a single observation, either the ACIS-S
(S) or coadded ACIS-I (I)) variable;
MV = source flux varies significantly between the sequential ACIS-I
observations;
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 2 I2 --- GC Running identification number
(<[PRF2009] NN> in Simbad)
4- 11 F8.4 deg RAXdeg X-ray Right Ascension in decimal degrees (J2000)
13- 18 F6.4 deg DEXdeg X-ray Declination in decimal degrees (J2000)
20- 23 F4.2 arcsec Offset from NGC 4636 center
25- 29 I5 --- CTIO Dirsch et al. (2005, Cat. J/A+A/433/43) CTIO
identification number
31- 39 F9.5 deg RAOdeg Optical Right Ascension in decimal degrees
(J2000)
41- 47 F7.5 deg DEOdeg Optical Declination in decimal degrees (J2000)
49- 52 F4.2 mag C-R The (C-R) color index (Washington C (blue) minus
Kron-Cousins R)
54- 58 F5.2 mag Rmag The Kron-Cousins R band magnitude
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Nomenclature Notes:
In table 2, sources are <[PRF2009] DDD.dddd+D.dddd> in Simbad.
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 29-Apr-2011