THE HERSCHEL EXPLOITATION OF LOCAL GALAXY ANDROMEDA (HELGA). VI. THE DISTRIBUTION AND PROPERTIES OF MOLECULAR CLOUD ASSOCIATIONS IN M31

Journal Article · Thu Jan 01 00:00:00 EST 2015 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/798/1/58· OSTI ID:22364705

Kirk, J. M. ^[1]; Gear, W. K.; Smith, M. W. L.; Ford, G.; Eales, S. A.; Gomez, H. L. ^[2]; Fritz, J.; Baes, M.; De Looze, I.; Gentile, G.; Gordon, K.; Verstappen, J.; Viaene, S. ^[3]; Bendo, G. J. ^[4]; O'Halloran, B. ^[5]; Madden, S. C.; Lebouteiller, V. ^[6]; Roman-Duval, J. ^[7]; Boselli, A. ^[8]; Cooray, A. ^[9] ; others, and

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1. Jeremiah Horrocks Institute, University of Central Lancashire, Preston PR1 2HE (United Kingdom)
2. School of Physics and Astronomy, Cardiff University, Queens Buildings, The Parade, Cardiff, Wales CF24 3AA (United Kingdom)
3. Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium)
4. UK ALMA Regional Centre Node, Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL (United Kingdom)
5. Astrophysics Group, Imperial College, Blackett Laboratory, Prince Consort Road, London SW7 2AZ (United Kingdom)
6. Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, Irfu/Service, Paris, F-91190 Gif-sur-Yvette (France)
7. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
8. Laboratoire d'Astrophysique de Marseille, UMR 7326 CNRS, 38 rue F. Joliot-Curie, F-13388 Marseille (France)
9. Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States)

In this paper we present a catalog of giant molecular clouds (GMCs) in the Andromeda (M31) galaxy extracted from the Herschel Exploitation of Local Galaxy Andromeda (HELGA) data set. GMCs are identified from the Herschel maps using a hierarchical source extraction algorithm. We present the results of this new catalog and characterize the spatial distribution and spectral energy properties of its clouds based on the radial dust/gas properties found by Smith et al. A total of 326 GMCs in the mass range 10{sup 4}-10{sup 7} M {sub ☉} are identified; their cumulative mass distribution is found to be proportional to M {sup –2.34}, in agreement with earlier studies. The GMCs appear to follow the same correlation of cloud mass to L {sub CO} observed in the Milky Way. However, comparison between this catalog and interferometry studies also shows that the GMCs are substructured below the Herschel resolution limit, suggesting that we are observing associations of GMCs. Following Gordon et al., we study the spatial structure of M31 by splitting the observed structure into a set of spiral arms and offset rings. We fit radii of 10.3 and 15.5 kpc to the two most prominent rings. We then fit a logarithmic spiral with a pitch angle of 8.°9 to the GMCs not associated with either ring. Last, we comment on the effects of deprojection on our results and investigate the effect different models for M31's inclination will have on the projection of an unperturbed spiral arm system.

• OSTI ID: 22364705
• Journal Information: Astrophysical Journal, Vol. 798, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ALGORITHMS
CATALOGS
CLOUDS
COMPARATIVE EVALUATIONS
CORRELATIONS
COSMIC DUST
INCLINATION
INTERFEROMETRY
MASS
MASS DISTRIBUTION
MILKY WAY
RESOLUTION