J/ApJ/721/1368 X-ray emission from the Sombrero galaxy (Li+, 2010)
X-ray emission from the Sombrero galaxy: discrete sources.
Li Z., Spitler L.R., Jones C., Forman W.R., Kraft R.P., Stefano R.D.,
Tang S., Wang Q.D., Gilfanov M., Revnivtsev M.
<Astrophys. J., 721, 1368-1382 (2010)>
=2010ApJ...721.1368L 2010ApJ...721.1368L
ADC_Keywords: Clusters, globular ; Galaxies, nearby ; X-ray sources
Keywords: galaxies: individual (M104) - galaxies: spiral - X-rays: binaries -
X-rays: galaxies
Abstract:
We present a study of discrete X-ray sources in and around the
bulge-dominated, massive Sa galaxy, Sombrero (M104), based on new and
archival Chandra observations with a total exposure of ∼200ks. With a
detection limit of LX∼1037erg/s and a field of view covering a
galactocentric radius of ∼30kpc (11.5'), 383 sources are detected.
Cross-correlation with Spitler et al.'s catalog of Sombrero globular
clusters (GCs) (Cat. J/AJ/132/1593) identified from HST/ACS
observations reveals 41 X-ray sources in GCs, presumably low-mass
X-ray binaries (LMXBs). We quantify the differential luminosity
functions (LFs) for both the detected GC and field LMXBs, whose
power-law indices (∼1.1 for the GC-LF and ∼1.6 for field-LF) are
consistent with previous studies for elliptical galaxies. With precise
sky positions of the GCs without a detected X-ray source, we further
quantify, through a fluctuation analysis, the GC-LF at fainter
luminosities down to 1035erg/s. We also detect 101 sources in the
halo of Sombrero. The presence of these sources cannot be interpreted
as galactic LMXBs whose spatial distribution empirically follows the
starlight. Their number is also higher than the expected number of
cosmic active galactic nuclei (52±11 [1σ]) whose surface
density is constrained by deep X-ray surveys.
Description:
Existing Chandra studies of X-ray sources in Sombrero (Di Stefano et
al. 2003, Cat. J/ApJ/599/1067; Kundu et al. 2007, Cat. J/ApJ/662/525;
Li et al. 2007, Cat. J/MNRAS/376/960) are based on a 19ks ACIS-S
observation taken on 2001 May 31 (ObsID 1586; PI: S. Murray). On April
29 and 2008 December 2, we obtained two new Chandra ACIS-I
observations (ObsIDs 9532 and 9533; PI: C. Jones), with exposures of
85 and 90ks, respectively. In this work, we utilize data from all
three observations.
Hubble Space Telescope (HST)/Advance Camera for Surveys (ACS) data in
the "science-ready form" were used by Spitler et al. (S06; 2006, Cat.
J/AJ/132/1593) to identify GC candidates in a ∼600"x400" six-pointing
mosaic centered on Sombrero. Three optical bands (BVR) were obtained
through the Hubble Heritage Project (PI: K. Noll, PID 9714). S06 used
photometric and size selection (GCs are partially resolved on the ACS
imaging) to construct a catalog of 659 GC candidates. Owing to the
excellent quality of the HST images, the catalog contains all but the
faintest 5% of the GCs in this field, with minimal contamination. In
particular, objects falling on Sombrero's prominent dust lane are
excluded. Here, we use improved photometric measurements for the GC
candidates (see discussion in Spitler et al. 2008, Cat.
J/MNRAS/389/1150).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 128 383 Chandra source list
table2.dat 91 229 List of sources detected from ObsID 1586
table3.dat 91 325 List of sources detected from ObsID 9532
table4.dat 91 329 List of sources detected from ObsID 9533
table5.dat 47 41 List of X-ray sources associated with Sombrero
globular clusters (most likely LMXBs)
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See also:
J/MNRAS/401/1965 : Globular clusters in M104 (Harris+, 2010)
J/MNRAS/389/1150 : Spitzer photometry of GCs in 2 galaxies (Spitler+, 208)
J/ApJ/658/980 : New velocities for 62 GCs in M104 (Bridges+, 2007)
J/MNRAS/376/960 : X-ray in the Sombrero galaxy (NGC 4594) (Li+, 2007)
J/ApJ/662/525 : LMXBs in globular clusters of 5 galaxies (Kundu+, 2007)
J/AJ/132/1593 : BVR photometry of NGC 4594 GCs (Spitler+, 2006)
J/ApJ/599/1067 : X-ray sources in M104 (Di Stefano+, 2003)
J/MNRAS/327/1116 : VI photometry of Sombrero globular clusters (Larsen+, 2001)
J/ApJ/458/455 : M 104 planetary nebulae (Ford+ 1996)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/383] Generic source number (not as in other
tables)
5- 23 A19 --- CXOU CXOU source name (JHHMMSS.ss+DDMMSS.s) (G1)
25- 27 F3.1 arcsec e_pos [0/2.4] The 1σ positional uncertainty (1)
29- 34 F6.2 ct/s CR On-axis source F-band count rate (0.4-6keV) (G2)
36- 39 F4.2 ct/s e_CR Uncertainty in CR
41- 45 F5.2 ct/s CR1 The 0.4-0.7keV band count rate (S1)
47- 50 F4.2 ct/s e_CR1 Uncertainty in CR1
52- 56 F5.2 ct/s CR2 The 0.7-1keV band count rate (S2)
58- 61 F4.2 ct/s e_CR2 Uncertainty in CR2
63- 67 F5.2 ct/s CR3 The 1-2keV band count rate (H1)
69- 72 F4.2 ct/s e_CR3 Uncertainty in CR3
74- 78 F5.2 ct/s CR4 The 2-6keV band count rate (H2)
80- 83 F4.2 ct/s e_CR4 Uncertainty in CR4
85- 89 F5.2 --- HR Hardness ratio (H2-M-S1)/(H2+M+S1) (G3)
91- 94 F4.2 --- e_HR Uncertainty in HR
96-100 F5.2 --- HR1 Hardness ratio (M-S1)/(M+S1) (G3)
102-105 F4.2 --- e_HR1 Uncertainty in HR1
107-111 F5.2 --- HR2 Hardness ratio (H2-H1)/(H2+H1) (G3)
113-116 F4.2 --- e_HR2 Uncertainty in HR2
118-128 A11 --- Flag Band(s) in which a source is detected (G3)
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Note (1): Calculated from the maximum likelihood centroiding.
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Byte-by-byte Description of file: table[234].dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/329] Generic source number within the table
5- 23 A19 --- CXOU CXOU source name (JHHMMSS.ss+DDMMSS.s) (G1)
25- 30 F6.2 ct/s CR On-axis source F-band count rate (G2)
32- 35 F4.2 ct/s e_CR Uncertainty in CR
37- 41 F5.2 ct/s CR1 The 0.4-0.7keV band count rate (S1)
43- 46 F4.2 ct/s e_CR1 Uncertainty in CR1
48- 52 F5.2 ct/s CR2 The 0.7-1keV band count rate (S2)
54- 57 F4.2 ct/s e_CR2 Uncertainty in CR2
59- 63 F5.2 ct/s CR3 The 1-2keV band count rate (H1)
65- 68 F4.2 ct/s e_CR3 Uncertainty in CR3
70- 74 F5.2 ct/s CR4 The 2-6keV band count rate (H2)
76- 79 F4.2 ct/s e_CR4 Uncertainty in CR4
81- 91 A11 --- Flag Band(s) in which a source is detected (G3)
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [46/346] Generic X-ray source number (as in
table 1)
5- 13 F9.5 deg RAdeg Right ascension in decimal degrees (J2000)
15- 23 F9.5 deg DEdeg Declination in decimal degrees (J2000)
25- 29 F5.2 mag Bmag B-band apparent magnitude
31- 35 F5.2 mag Vmag V-band apparent magnitude
37- 41 F5.2 mag Rmag R-band apparent magnitude
43- 47 F5.3 zW Fx 0.3-8keV intrinsic flux in 10-14erg/s
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Global notes:
Note (G1): The unregistered source name follows the Chandra naming convention
and the IAU Recommendation for Nomenclature (e.g.,
http://cds.u-strasbg.fr/iau-spec.html).
Note (G2): The sum of the exposure-corrected count rates in the four bands,
based on the merged data of the three observations.
Note (G3): Band(s) are S1, S2, H1, H2 and combinations B, M, H, S:
S1 = 0.4-0.7keV
S2 = 0.7-1keV
H1 = 1-2keV
H2 = 2-6keV
B = S1+S2+H1+H2 (broad 0.4-6keV)
M = S2+H1 (medium 0.7-2keV)
H = H1+H2 (hard 1-6keV)
S = S1+S2 (soft 0.4-1keV)
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 09-Jul-2012