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J/ApJ/554/202 ROSAT X-ray observations of M81 (Immler+, 2001)
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ROSAT X-ray observations of the spiral galaxy M81.
Immler S., Wang Q.D.
<Astrophys. J. 554, 202 (2001)>
=2001ApJ...554..202I
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ADC_Keywords: X-ray sources ; Radio sources
Keywords: galaxies: individual (M81) - galaxies: general - galaxies: spiral -
X-rays: galaxies - X-rays: general - X-rays: ISM
Abstract:
We present results from the analysis of deep ROSAT HRI and PSPC
observations of the spiral galaxy M81. The inferred total (0.5-2keV
band) luminosity of M81 is ~3x10^40^ergs/s, excluding the contribution
from identified interlopers found within the D_25_ ellipse. The
nucleus of the galaxy alone accounts for about 65% of this luminosity.
The rest is due to 26 other X-ray sources (contributing ~10%) and to
apparently diffuse emission, which is seen across much of the galactic
disk and is particularly bright in the bulge region around the
nucleus. Spectral analysis further gives evidence for a soft
component, which can be characterized by a two-temperature optically
thin plasma with temperature at ~0.15 and 0.60keV and an absorption of
the galactic foreground only. These components, accounting for ~13% of
the X-ray emission from the region, apparently arise in a combination
of hot gas and faint discrete sources. We find interesting spatial
coincidences of luminous (10^37^-10^40^ergs/s) and variable X-ray
sources with shock-heated optical nebulae. Three of them are
previously classified as supernova remnant candidates. The other one
is far off the main body of M81 but is apparently associated with a
dense H I concentration produced most likely by the tidal interactions
of the galaxy with its companions. These associations suggest that
such optical nebulae may be powered by outflows from luminous X-ray
binaries, which are comparable to, or more luminous than, Galactic
"microquasars."
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 98 46 ROSAT HRI M81 source list
table4.dat 66 69 ROSAT PSPC M81 source list
table5.dat 61 30 ROSAT M81 source identifications
table6.dat 72 3 Position Coincidence between X-Ray sources and
SNR candidates
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See also:
IX/28 : ROSAT HRI Pointed Observations (1RXH) (ROSAT Team, 2000)
IX/30 : Second ROSAT PSPC Catalog (ROSAT, 2000)
IX/31 : The WGACAT version of ROSAT sources (White+ 2000)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- HNN Source name (where H denotes HRI) (G1)
5- 6 I2 h RAh Right Ascension (J2000)
8- 9 I2 min RAm Right Ascension (J2000)
11- 15 F5.2 s RAs Right Ascension (J2000)
17 A1 --- DE- Sign of the Declination (J2000)
18- 19 I2 deg DEd Declination (J2000)
21- 22 I2 arcmin DEm Declination (J2000)
24- 27 F4.1 arcsec DEs Declination (J2000)
29- 32 F4.1 arcsec R90% The 90% confidence error radius of the
source position (1)
34- 39 F6.1 10-4.ct/s CR Net count rate (2)
41- 44 F4.1 10-4.ct/s e_CR Uncertainty in CR (2)
46- 48 A3 --- Com Comment regarding source variability
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Note (1): Includes 3.5" systematic error for the attitude solution.
Note (2): Corrected for vignetting, exposure and dead-time.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- PNN Source name (where `P' denotes PSPC) (G1)
5- 6 I2 h RAh Right Ascension (J2000)
8- 9 I2 min RAm Right Ascension (J2000)
11- 14 F4.1 s RAs Right Ascension (J2000)
16 A1 --- DE- Sign of the Declination (J2000)
17- 18 I2 deg DEd Declination (J2000)
20- 21 I2 arcmin DEm Declination (J2000)
23- 24 I2 arcsec DEs Declination (J2000)
26- 30 F5.1 ct/ks CR Net count rate in the 0.5-2keV band
32- 34 F3.1 ct/ks e_CR Uncertainty in CR
36- 40 F5.2 --- HR1 First hardness ratio (1)
42- 45 F4.2 --- e_HR1 Uncertainty in HR1
47- 51 F5.2 --- HR2 Second hardness ratio (2)
53- 56 F4.2 --- e_HR2 Uncertainty in HR2
58- 65 A8 --- Com Further HRI source positional coincidences
and variability comments
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Note (1): Defined as HR1=(hard-soft)/(hard+soft) where `soft' and `hard'
denote source net count rates in the 0.11-0.41keV and 0.52-2.01keV
bands, respectively.
Note (2): Defined as HR2=(hard2-hard1)/(hard2+hard1) and `hard1' and `hard2'
are the split of a hard-band rate into two 0.52-0.90keV and
0.91-2.01keV bands, respectively.
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- HNN HRI ROSAT name (HNN) (G1)
5- 7 A3 --- PNN PSPC ROSAT Name (PNN) (G1)
9- 12 F4.1 arcsec Offset Offset from the X-ray position
14- 18 F5.2 mag Rmag ? R magnitude
20- 24 F5.2 mag Bmag ? B magnitude
26 A1 --- l_B-R Limit flag on B-R
27- 31 F5.2 mag B-R ? B-R colour index
33- 62 A30 --- Id Identification (1)
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Note (1): Identifications:
GS: HST Guide Star Catalog v1.1, Cat. <I/220>
U: USNO A-v2.0 Catalog of Astrometric Standards, Cat. <I/252>
MF: SNR candidate number from Matonick & Fesen, 1997ApJS..112...49M
[MF97] M 81 NN in Simbad
X: Einstein X-ray source number from Fabbiano, 1988ApJ...325..544F
[F88] X-NN in Simbad
Ho IX: Holmberg IX dwarf galaxy.
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- [MF97] SNR designation
(MF NN = [MF97] M 81 NN in Simbad)
7- 8 I2 h RAh Right Ascension (J2000)
10- 11 I2 min RAm Right Ascension (J2000)
13- 16 F4.1 s RAs Right Ascension (J2000)
18 A1 --- DE- Sign of the Declination (J2000)
19- 20 I2 deg DEd Declination (J2000)
22- 23 I2 arcmin DEm Declination (J2000)
25- 28 F4.1 arcsec DEs Declination (J2000)
30- 32 F3.1 arcsec Offset Offset between X-ray and optical positions
34- 40 E7.1 W LHa H{alpha} luminosity
42- 45 F4.2 --- [SII]/Ha Ratio of [SII] to H{alpha}
47- 48 I2 pc Size Size
50- 56 A7 --- Opt Optical shape
58- 60 A3 --- HNN HRI ROSAT source name (G1)
61 A1 --- --- [/]
62- 64 A3 --- PNN PSPC ROSAT source name (G1)
66- 72 E7.1 W LX X-ray luminosity
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Global notes:
Note (G1): Designations in Simbad:
HNN = <[IW2001] HNN>
PNN = <[IW2001] PNN>
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History:
From electronic version of the journal
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(End) Greg Schwarz [AAS], Patricia Bauer [CDS] 10-Sep-2001