J/ApJ/777/7 Chandra observations of 8 bulgeless disk galaxies (Somers+, 2013)
Discovery of a large population of ultraluminous X-ray sources in the bulgeless
galaxies NGC 337 and ESO 501-23.
Somers G., Mathur S., Martini P., Watson L., Grier C.J., Ferrarese L.
<Astrophys. J., 777, 7 (2013)>
=2013ApJ...777....7S 2013ApJ...777....7S
ADC_Keywords: X-ray sources ; Galaxies, nearby ; Cross identifications
Keywords: galaxies: nuclei; X-rays: binaries; X-rays: galaxies
Abstract:
We have used Chandra observations of eight bulgeless disk galaxies to
identify new ultraluminous X-ray source (ULX) candidates, study their
high-mass X-ray binary (HMXB) population, and search for
low-luminosity active galactic nuclei (AGNs). We report the discovery
of 16 new ULX candidates in our sample of galaxies. Eight of these are
found in the star forming galaxy NGC 337, none of which are expected
to be background contaminants. The HMXB luminosity function of NGC 337
implies a star formation rate (SFR) of 6.8-3.5+4.4M_☉/yr,
consistent at 1.5σ with a recent state of the art SFR
determination. We also report the discovery of a bright ULX candidate
(X-1) in ESO 501-23. X-1's spectrum is well fit by an absorbed power
law with Γ=1.18-0.11+0.19 and NH=1.13-1.13+7.07/cm2,
implying a 0.3-8keV flux of 1.08-0.07+0.05x10-12erg/s/cm2. Its
X-ray luminosity (LX) is poorly constrained due to uncertainties in
the host galaxy's distance, but we argue that its spectrum implies
LX>1040erg/s. An optical counterpart to this object may be present
in an Hubble Space Telescope image. We also identify ULX candidates in
IC 1291, PGC 3853, NGC 5964, and NGC 2805. We find no evidence of
nuclear activity in the galaxies in our sample, placing a flux upper
limit of 4x10-15erg/s/cm2 on putative AGN. Additionally, the Type
II-P supernova SN 2011DQ in NGC 337, which exploded two months before
our X-ray observation, is undetected.
Description:
The observations were undertaken with the Chandra X-Ray Observatory
Advanced CCD Imaging Spectrometer (ACIS) between 2010 November and
2012 January.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 82 8 Galaxy properties
table3.dat 94 174 Full X-ray source list
table4.dat 97 44 USNO-B1.0 cross-correlation
table5.dat 133 57 SDSS-DR8 cross-correlation
table6.dat 121 62 WISE cross-correlation
table7.dat 142 40 Sources consistent with ULX in the sample galaxies
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See also:
B/chandra : The Chandra Archive Log (CXC, 1999-2014)
V/139 : The SDSS Photometric Catalog, Release 9 (Adelman-McCarthy+, 2012)
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
II/306 : The SDSS Photometric Catalog, Release 8 (Adelman-McCarthy+, 2011)
VIII/76 : Leiden/Argentine/Bonn (LAB) Survey of Galactic HI (Kalberla+ 2005)
VII/237 : HYPERLEDA. I. Catalog of galaxies (Paturel+, 2003)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
VII/155 : Third Reference Cat. of Bright Galaxies (RC3) (de Vaucouleurs+ 1991)
VII/145 : Nearby Galaxies Catalogue (NBG) (Tully 1988)
J/ApJ/741/49 : ULX candidates in nearby galaxies (Swartz+, 2011)
J/ApJ/687/471 : Observational comparison between ULXs and XRBs (Berghea+, 2008)
J/ApJ/676/184 : Peculiar motion away from the Local Void (Tully+, 2008)
J/ApJ/649/730 : ULX population in nearby galaxies from XMM (Winter+, 2006)
J/ApJS/164/81 : Spectrophotometry of nearby galaxies (Moustakas+, 2006)
J/AJ/126/1607 : IRAS Revised Bright Galaxy Sample (Sanders+, 2003)
http://www.sdss3.org/ : SDSS-III home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- Name Galaxy name
12- 13 I2 h RAh Hour of right ascension (J2000) (1)
15- 16 I2 min RAm Minute of right ascension (J2000)
18- 22 F5.2 s RAs Second of right ascension (J2000)
24 A1 --- DE- Sign of declination (J2000) (1)
25- 26 I2 deg DEd Degree of declination (J2000) (1)
28- 29 I2 arcmin DEm Arcminute of declination (J2000)
31- 34 F4.1 arcsec DEs Arcsecond of declination (J2000)
36- 39 F4.2 arcsec ePos [0.5/1.3] Positional uncertainty (1)
41- 45 F5.2 Mpc Dist [7/31.5] Distance to the galaxy
47- 49 A3 --- r_Dist Distance reference (2)
51- 53 I3 arcsec Maj [109/379] Semi-major axis of the 25th
magnitude/arcsec2 B-band isophote (3)
55- 57 I3 arcsec Min [87/287] Semi-minor axis of the 25th
magnitude/arcsec2 B-band isophote (3)
59- 63 F5.1 deg PA [105/300] Pitch angle of the galaxy,
from Watson et al. (2012ApJ...751..123W 2012ApJ...751..123W)
65- 67 F3.1 deg e_PA [0.2/5] PA uncertainty
69- 71 F3.1 --- TT [6.5/8] de Vaucouleurs (VII/155) T type
73- 76 F4.2 10+20/cm2 NH [0.9/7.4] Galactic hydrogen column density
along line-of-sight to galaxy (4)
78- 82 F5.2 [10-7W] AGN [37.3/38.7] log 2σ upper limit for a
putative AGN luminosity at the location
from RA and DEC
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Note (1): RA and DEC of galactic nucleus with uncertainties, taken from 2MASS,
SDSS (UGC 6446, NGC 3794) and 6dF (ESO 501-23). These are typically
photometric centers; see Watson et al. 2011ApJS..194...36W 2011ApJS..194...36W, for
rotational centers.
Note (2): Reference as follows:
T88 = Tully, R. B. 1988, Nearby Galaxies Catalog (Cat. VII/145)
T08 = Tully et al. 2008, Cat. J/ApJ/676/184
Note (3): From de Vaucouleurs et al. (1991, Cat. VII/155)
Note (4): From Kalberla et al. (2005, Cat. VIII/76)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- ObsID [12979/12986] Chandra observation ID (1)
7- 8 A2 --- Chip ACIS-S chip number (S2-S4)
10- 12 I3 --- Seq [1/174] Running sequence number
14- 29 A16 --- CXOU Chandra X-ray source name (JHHMMSS.s+DDMMSS)
31- 32 I2 h RAh Hour of right ascension (J2000)
34- 35 I2 min RAm Arcminute of right ascension (J2000)
37- 40 F4.1 s RAs Second of right ascension (J2000)
42 A1 --- DE- Sign of declination (J2000)
43- 44 I2 deg DEd Degree of declination (J2000)
46- 47 I2 arcmin DEm Arcminute of declination (J2000)
49- 50 I2 arcsec DEs Arcsecond of declination (J2000)
52- 54 I3 cm2 Aeff [102/655] 1.7keV effective area at the
location of the source (2)
56- 59 F4.1 arcmin Delta [0/13] Angular distance Δ from the pointing
location of the observation to the source
61- 65 F5.1 ct Bcts [4/867] Net counts in the 0.3-8keV band (3)
67- 70 F4.1 ct e_Bcts [2/30] Ncts 1σ uncertainty (3)
72- 76 F5.1 ct Scts [0/529] Net counts in the 0.3-2keV band (3)
78- 81 F4.1 ct e_Scts [0/23] Scts 1σ uncertainty (3)
83- 87 F5.1 ct Hcts [-3/339] Net counts in the 2-8keV band (3)
89- 92 F4.1 ct e_Hcts [0.1/19] Hcts 1σ uncertainty (3)
94 A1 --- D25? [Y] Is this object within the D25 isophote of
the target galaxy?
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Note (1): The Chandra observation ID of the exposure that found this source, as
well as the target galaxy of that observation.
Note (2): This is the net instrument response, integrated over the dither path
of the observation. Sources with lower effective areas are typically
on CCD chip edges.
Note (3): Background subtracted net counts in broad (0.3-8keV), soft (0.3-2keV)
and hard (2-8keV) bands respectively.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/172]? Sequence number as in table 3
5- 9 I5 --- ObsID [12979/12986] Observation ID
11 I1 --- Chip [6/8] CCD chip number
13- 14 I2 --- WNum Wavdetect source number
16- 27 A12 --- USNO-B1.0 USNO-B1.0 identifier
29- 32 F4.2 arcsec Delta [0.08/2] Offset between X-ray source and
USNO-B1.0 source centroid
34- 38 F5.2 mag B1mag [10.9/21.3]? First USNO-B1 B-band magnitude
40- 44 F5.2 mag R1mag [9.4/20.3]? First USNO-B1 R-band magnitude
46- 50 F5.2 mag B2mag [10.3/21.9]? Second USNO-B1 B-band magnitude
52- 56 F5.2 mag R2mag [9.3/20.8]? Second USNO-B1 R-band magnitude
58- 62 F5.2 mag Imag [8.9/18.8]? USNO-B1 I-band magnitude
64- 65 I2 h RAh USNO-B1 hour of right ascension (J2000)
67- 68 I2 min RAm Minute of right ascension (J2000)
70- 75 F6.3 s RAs Second of right ascension (J2000)
77 A1 --- DE- USNO-B1 sign of declination (J2000)
78- 79 I2 deg DEd USNO-B1 degree of declination (J2000)
81- 82 I2 arcmin DEm Arcminute of declination (J2000)
84- 88 F5.2 arcsec DEs Arcsecond of declination (J2000)
90- 93 I4 mas/yr pmRA [-142/12] USNO-B1 proper motion along RA
95- 97 I3 mas/yr pmDE [-62/12] USNO-B1 proper motion along DEC
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/173] Sequence number as in table 3
5- 9 I5 --- ObsID [12979/12986] Observation ID
11 I1 --- Chip [6/8] CCD chip number
13- 14 I2 --- WNum [1/19] Wavdetect source number
16- 34 A19 --- SDSS SDSS-DR8 identification (JHHMMSS.ss+DDMMSS.s)
36- 40 F5.3 arcsec Delta [0.1/2] Offset Δ between centroid of
Chandra source and SDSS DR8 source
42- 47 F6.3 mag umag [14.5/27.7] SDSS-DR8 u-band magnitude
49- 53 F5.3 mag e_umag [0.005/4] umag uncertainty
55- 60 F6.3 mag gmag [10.8/31] SDSS-DR8 g-band magnitude
62- 66 F5.3 mag e_gmag [0.001/0.7] gmag uncertainty
68- 73 F6.3 mag rmag [9.9/30.2] SDSS-DR8 r-band magnitude
75- 79 F5.3 mag e_rmag [0.001/0.7] rmag uncertainty
81- 86 F6.3 mag imag [9.7/24.3] SDSS-DR8 i-band magnitude
88- 92 F5.3 mag e_imag [0.001/0.9] imag uncertainty
94- 99 F6.3 mag zmag [9.8/27.7] SDSS-DR8 z-band magnitude
101-105 F5.3 mag e_zmag [0.001/2] zmag uncertainty
107-108 I2 h RAh SDSS-DR8 hour of right ascension (J2000)
110-111 I2 min RAm SDSS-DR8 minute of right ascension (J2000)
113-118 F6.3 s RAs SDSS-DR8 second of right ascension (J2000)
120 A1 --- DE- SDSS-DR8 sign of declination (J2000)
121-122 I2 deg DEd SDSS-DR8 degree of declination (J2000)
124-125 I2 arcmin DEm SDSS-DR8 arcminute of declination (J2000)
127-131 F5.2 arcsec DEs SDSS-DR8 arcsecond of declination (J2000)
133 I1 --- Cl [3/6] SDSS-DR8 object class (3=galaxy, 6=star)
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 I3 --- Seq [1/173] Sequence number as in table 3
5- 9 I5 --- ObsID [12979/12986] Observation ID
11 I1 --- Chip [6/8] CCD chip number
13- 14 I2 --- WNum Wavdetect source number
16- 34 A19 --- WISE WISE identification (JHHMMSS.ss+DDMMSS.s)
36- 40 F5.3 arcsec Delta [0.09/2] Offset between centroid of Chandra
source and WISE source
42- 47 F6.3 mag W1mag [7.5/17.9] WISE W1-band magnitude
49- 53 F5.3 mag e_W1mag [0.02/0.3] W1mag uncertainty
55- 60 F6.3 mag W2mag [7.6/16.9] WISE W2-band magnitude
62- 66 F5.3 mag e_W2mag [0.02/0.5] W2mag uncertainty
68 A1 --- l_W3mag Limit flag on W3mag
70- 75 F6.3 mag W3mag [6.7/13.4] WISE W3-band magnitude
77- 81 F5.3 mag e_W3mag [0.01/0.6]? W3mag uncertainty
83 A1 --- l_W4mag Limit flag on W4mag
85- 89 F5.3 mag W4mag [3.7/9.8] WISE W4-band magnitude
91- 95 F5.3 mag e_W4mag [0.01/0.6]? W4mag uncertainty
97- 98 I2 h RAh Hour of right ascension (J2000)
100-101 I2 min RAm Minute of right ascension (J2000)
103-108 F6.3 s RAs Second of right ascension (J2000)
110 A1 --- DE- Sign of declination (J2000)
111-112 I2 deg DEd Degree of declination (J2000)
114-115 I2 arcmin DEm Arcminute of declination (J2000)
117-121 F5.2 arcsec DEs Arcsecond of declination (J2000)
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Byte-by-byte Description of file: table7.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Name Galaxy name
12- 15 A4 --- XID X-ray identifier (X-NN)
17- 19 I3 --- Seq [5/145] Sequence number as in table 3
21- 36 A16 --- CXOU Chandra ID name (JHHMMSS.s+DDMMSS)
38- 42 F5.1 arcsec Dist [2.2/168] Projected distance from
galactic nucleus
44- 48 F5.1 ct Bcts [4.4/867] Net broad (0.3-8keV) detected counts
within 2.3" aperture
50- 53 F4.1 ct e_Bcts [2.2/29.5] Bcts uncertainty
55- 59 F5.1 ct Scts [1/528.7] Net soft (0.3-2keV) detected counts
within 2.3" aperture
61- 64 F4.1 ct e_Scts [1/23] Scts uncertainty
66- 70 F5.1 ct Hcts [-0.3/338.3] Net hard (2-8keV) detected counts
within 2.3" aperture
72- 75 F4.1 ct e_Hcts [0.1/18.4] Hcts uncertainty
77- 81 F5.2 --- HR [-1.09/0.6] Hardness ratio: (H-S)/(H+S) (1)
83- 86 F4.2 --- e_HR [0.03/0.5] Gaussian error of HR (1)
88- 91 F4.2 --- Gamma [0.1/3.1]? Approximate value of the power law
exponent Γ (2)
93- 96 F4.2 --- E_Gamma ? Positive error on Gamma
98-101 F4.2 --- e_Gamma ? Negative error on Gamma
103-107 F5.2 10-17W/m2 Flux [0.43/84.7] Unabsorbed flux
in 10-14erg/s/cm2 (3)
109-112 F4.2 10-17W/m2 e_Flux [0.2/2.9] Flux uncertainty
114-119 F6.2 10+31W LX [0.4/167] X-ray luminosity of the source (4)
121-125 F5.2 10+31W e_LX [0.1/11] LX uncertainty
127 A1 --- Ha? [Y] Does this object coincide with Hα
emission from MDM imaging?
129-142 A14 --- Note Notes (5)
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Note (1): These are calculated using background subtracted count values, so
they may not precisely map to other values in this table.
Note (2): Approximate value of the power law exponent (Γ) that would
produce the observed ratio of hard to soft counts.
Note (3): Unabsorbed flux, in units of 10-14erg/s/cm2, calculated in PIMMS
with a Γ=1.7 power law, including galactic absorption. Source
counts were extracted from the 0.3-8keV band, and extrapolated to
0.3-10keV.
Note (4): Inferred luminosity of the source, at the galactic distance, in units
of 1038erg/s. This is only valid for sources that are in fact
associated with the galaxy.
Note (5): Notes are!
ULX = indicates a ULX candidate;
(a) = indicates a match in the UNSO-B1.0 catalog,
(b) = indicates a match in the WISE point source catalog,
(c) = indicates a match in the SDSS DR8 catalog.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 26-Mar-2015