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The Herschel exploitation of local galaxy andromeda (HELGA). VI. the distribution and properties of molecular cloud associations in m31

Kirk, J. M., Gear, Walter, Fritz, J., Smith, Matthew William L., Ford, G., Baes, M., Bendo, G. J., De Looze, I., Eales, Stephen Anthony, Gentile, G., Gomez, Haley Louise, Gordon, K., O'Halloran, B., Madden, S. C., Roman-Duval, J., Verstappen, J., Viaene, S., Boselli, A., Cooray, A., Lebouteiller, V. and Spinoglio, L. 2015. The Herschel exploitation of local galaxy andromeda (HELGA). VI. the distribution and properties of molecular cloud associations in m31. The Astrophysical Journal 798 (1) , pp. 58-76. 10.1088/0004-637X/798/1/58

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Abstract

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 104–107M� are identified; their cumulative mass distribution is found to be proportional to M −2.34, in agreement with earlier studies. The GMCs appear to follow the same correlation of cloud mass to LCO 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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: galaxies: individual (M31); galaxies: ISM; galaxies: structure; ISM: clouds
Publisher: IOP Science
ISSN: 1538-4357
Date of First Compliant Deposit: 14 July 2017
Date of Acceptance: 10 September 2014
Last Modified: 03 Jul 2019 04:04
URI: http://orca-mwe.cf.ac.uk/id/eprint/102417

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