J/ApJ/654/240 Giant molecular clouds in M31 (Rosolowsky+, 2007)
Giant molecular clouds in M31. I. Molecular cloud properties.
Rosolowsky E.
<Astrophys. J., 654, 240-251 (2007)>
=2007ApJ...654..240R 2007ApJ...654..240R
ADC_Keywords: Galaxies, nearby ; Molecular clouds ; Radio lines
Keywords: galaxies: individual (Andromeda) - galaxies: ISM - ISM: clouds -
radio lines: ISM
Abstract:
We present Berkeley-Illinois-Maryland Association (BIMA) millimeter
interferometer observations of giant molecular clouds (GMCs) along a
spiral arm in M31. The observations consist of a survey using the
compact configuration of the interferometer and follow-up, higher
resolution observations on a subset of the detections in the survey.
The data are processed using an analysis algorithm designed to extract
GMCs and correct their derived properties for observational biases,
thereby facilitating comparison with Milky Way data. The algorithm
identifies 67 GMCs, of which 19 have a sufficient signal-to-noise
ratio to accurately measure their properties. The GMCs in this portion
of M31 are indistinguishable from those found in the Milky Way, having
a similar size-line width relationship and distribution of virial
parameters, confirming the results of previous, smaller studies. The
velocity gradients and angular momenta of the GMCs are comparable to
the values measured in M33 and the Milky Way, and in all cases are
below expected values based on the local galactic shear. The studied
region of M31 has an interstellar radiation field, metallicity, Toomre
Q parameter, and midplane volume density similar to those of the inner
Milky Way, so the similarity of GMC populations between the two
systems is not surprising.
Description:
We observed 12CO (J=1->0) emission from M31 during the spring and
fall observing seasons of 2002 with the D and C configurations of the
BIMA millimeter interferometer
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 43 67 Molecular Cloud Properties in M31
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1 A1 --- Type [HL] (H)igh or (L)ow S/N Clouds (5)
3- 4 I2 --- [R2007] Sequential number
6- 10 I5 arcsec oRA Relative position along RA (1)
12- 16 I5 arcsec oDE Relative position along DE (1)
18- 19 I2 10+4solMass Mlum Luminous mass (2)
21- 22 I2 pc Re ? Deconvolved radius (2) (3)
24- 27 F4.2 km/s sigmav Line width (2)
29- 32 F4.1 --- Tmax/sigma Maximum temperature to line width rms ratio
34- 37 F4.2 km/s/pc |∇v| Velocity gradient magnitude (2)
38 A1 --- u_|∇v| [d] Uncertainty flag on |∇v| (4)
40- 43 I4 deg ∇PA Gradient position angle (2)
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Note (1): Position given in arcseconds relative to the center of M31 at
RA=00:42:44.3, DE=+41:16:09 (J2000)
Note (2): Typical errors in properties:
* luminous mass (MLum), 20%
* radius (Re), 15%
* line width (sigmav), 15%
* velocity gradient magnitude (|∇v|), 50%
* gradient position angle (φ∇).
Note (3): No values of the deconvolved radius (Re) are reported if the
cloud cannot be resolved with the present data.
Note (4): d = The uncertainty in the gradient of this cloud is larger than
0.15km/s/pc and it is not included in the gradient analysis.
Note (5): High S/N clouds have Tmax/sigma≥10.
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 25-Nov-2008