J/ApJS/144/213 Chandra X-ray observations of M81 (Swartz+, 2003)
Chandra X-ray observations of the spiral galaxy M81.
Swartz D.A., Ghosh K.K., McCollough M.L., Pannuti T.G., Tennant A.F., Wu K.
<Astrophys. J. Suppl. Ser. 144, 213 (2003)>
=2003ApJS..144..213S 2003ApJS..144..213S
ADC_Keywords: Galaxies, photometry ; X-ray sources
Mission_Name: Chandra
Keywords: galaxies: individual (M81) - supernovae: individual (SN 1993J) -
X-rays: binaries - X-rays: galaxies - X-rays: stars
Abstract:
A Chandra X-Ray Observatory ACIS-S imaging observation is used to
study the population of X-ray sources in the nearby Sab galaxy M81
(NGC 3031). A total of 177 sources are detected with 124 located
within the D25 isophote to a limiting X-ray luminosity of
∼3x1036erg/s. Source positions, count rates, luminosities in the
0.3-8.0 keV band, limiting optical magnitudes, and potential
counterpart identifications are tabulated. Spectral and timing
analysis of the 36 brightest sources are reported including the
low-luminosity active galactic nucleus, SN 1993J, and the
Einstein-discovered ultraluminous X-ray source X6.
Description:
The primary X-ray data set is a 49926s observation of M81 obtained on
2000 May 7 with the Chandra Advanced CCD Imaging Spectrometer (ACIS)
spectroscopy array operating in imaging mode. Unless otherwise noted,
references to X-ray data will refer to this data set. The X-ray data
were reprocessed by the Chandra X-ray Center (CXC) on 2001 January 4.
This reprocessed data are used in this work. There are no significant
differences between the reprocessed data and the originally
distributed data analyzed by Tennant et al. (2001ApJ...549L..43T 2001ApJ...549L..43T). The
observation was taken in faint timed exposure mode at 3.241s/frame at
a focal plane temperature of -120°C. Standard CXC processing has
applied aspect corrections and compensated for spacecraft dither.
The primary target, SN 1993J, was located near the nominal aimpoint on
the back-illuminated (BI) device S3. The nucleus of M81 lies 2.79' from
SN 1993J toward the center of S3 in this observation. Accurate
positions of these two objects and two G0 stars located on device S2
were used to identify any offset and to determine absolute locations
of the remaining Chandra sources as well as objects in other X-ray
images and those obtained at other wavelengths. No offset correction
was applied to the Chandra X-ray positions.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 99 177 M81 Discrete X-Ray Sources
table3.dat 50 33 M81 Bright X-Ray Sources
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See also:
J/ApJ/554/202 : ROSAT X-ray observations of M81 (Immler+, 2001)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- [SGM2003] The X-ray source number
5 I1 h RAh Hour of Right Ascension (J2000)
7- 8 I2 min RAm Minute of Right Ascension (J2000)
10- 14 F5.2 s RAs Second of Right Ascension (J2000)
15 A1 --- DE- Sign of Declination (J2000)
16- 17 I2 deg DEd Degree of Declination (J2000)
19- 20 I2 arcmin DEm Arcminute of Declination (J2000)
22- 25 F4.1 arcsec DEs Arcsecond of Declination (J2000)
27- 33 F7.2 10-4ct/s CRate Aperture-corrected number of source counts
35- 39 F5.2 10-4ct/s e_CRate Uncertainty in CRate
41- 46 F6.2 --- S/R Signal-to-Noise ratio for CRate
48 A1 --- l_Vmag Limit flag on Vmag
49- 53 F5.2 mag Vmag ? The visual magnitude (1)
55 A1 --- f_Vmag [HI] Flag on Vmag (2)
57- 58 A2 --- CCD CHANDRA ACIS CCD device identification
60- 64 A5 --- Region Global environment code (3)
66- 72 F7.2 10+30W XLum X-ray luminosity (4)
74- 79 F6.2 10+30W e_XLum Uncertainty in XLum
81- 98 A18 --- Com Additional comments (5)
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Note (1): From F555W, F606W, or F547M filter measurements and values
have not been corrected for charge transfer efficiency (CTE) effects
nor color-corrected to obtain true Johnson V magnitudes.
Note (2): Flag on Vmag:
H = located within HST field but without an optical candidate.
Fainter than the HST limiting magnitude of ∼27 magnitudes.
I = only F814W (I-band) image available
Note (3): Global environment code:
b = bulge
d = disk
D25 = source is outside the D25 isophote
Note (4): The unabsorbed luminosity in the 0.3-8.0keV energy range.
Note (5): X-ray detections from Einstein (denoted "X", Fabbiano,
1988ApJ...325..544F 1988ApJ...325..544F, [F88] X-NN in Simbad) and ROSAT ("P" and "H"
denoting PSPC- and HRI-identified sources, respectively, Immler &
Wang, 2001, Cat. J/ApJ/554/202, [IW2001] PNN and [IW2001] HNN in
Simbad), and potential source type based on spatial correlations with
catalogued objects or on other information (SSS means in Swartz et
al., 2002ApJ...574..382S 2002ApJ...574..382S) Explanations of the quantitative entries are
given in the text.
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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- 3 I3 --- [SGM2003] Sequential number
6- 9 F4.1 10+20cm-2 NH Hydrogen column density
11- 14 F4.1 10+20cm-2 e_NH rms uncertainty on NH
16- 19 F4.2 --- Sp-Index Spectral parameter (1)
21- 24 F4.2 --- e_Sp-Index rms uncertainty on SpPar
27- 31 F5.2 --- chi2 chi2 value
32 A1 --- --- [/]
33- 34 I2 --- DOF Degrees of freedom
36- 39 F4.1 10+30W XLum X-ray luminosity
41- 43 F3.1 10+30W e_XLum rms uncertainty on XLum
46- 50 F5.2 --- PKS Kolmogorov-Smirnov statistic result (2)
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Note (1): Power-law photon index, Γ, except for source numbers 160 and
161, where spectral parameter is blackbody temperature, kT, in keV.
Note (2): Sources with a low value of PKS have a high probability of
being variable
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 21-Feb-2003