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The role of spiral arms in Milky Way star formation

Ragan, S.E., Moore, T.J.T., Eden, D.J., Hoare, M.G., Urquhart, J.S., Elia, D., Molinari, S. (2018) The role of spiral arms in Milky Way star formation. Monthly Notices of the Royal Astronomical Society, 479 (2). pp. 2361-2373. ISSN 1365-2966. E-ISSN 1365-2966. (doi:10.1093/mnras/sty1672)

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Abstract

What role does Galactic structure play in star formation? We have used the Herschel Hi-GAL compact-clump catalogue to examine trends in evolutionary stage over large spatial scales in the inner Galaxy. We examine the relationship between the fraction of clumps with embedded star formation (the star-forming fraction, or SFF) and other measures of star-formation activity. Based on a positive correlation between SFF and evolutionary indicators such as the luminosity-to-mass ratio, we assert that the SFF principally traces the average evolutionary state of a sample and must depend on the local fraction of rapidly-evolving, high-mass young stellar objects. The spiralarm tangent point longitudes show small excesses in the SFF, though these can be accounted for by a small number of the most massive clusters, just 7.6% of the total number of clumps in the catalogue. This suggests that while the arms tend to be home to the Galaxy’s massive clusters, the remaining 92.4% of Hi-GAL clumps in our catalogue do not show an enhancement of star formation within arms. Globally, the SFF is highest at the Galactic midplane and inner longitudes. We find no significant trend in evolutionary stage as a function of position across spiral arms at the tangentpoint longitudes. This indicates that the angular offset observed between gas and stars, if coordinated by a density wave, is not evident at the clump phase; alternatively, the onset of star formation is not triggered by the spiral density wave.

Item Type: Article
DOI/Identification number: 10.1093/mnras/sty1672
Uncontrolled keywords: galaxies: ISM – ISM: clouds – stars: formation – ISM: structure – galaxies: ISM
Subjects: Q Science > QB Astronomy
Divisions: Faculties > Sciences > School of Physical Sciences > Centre for Astrophysics and Planetary Sciences
Depositing User: James Urquhart
Date Deposited: 22 Jun 2018 10:10 UTC
Last Modified: 12 Jul 2019 10:07 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/67396 (The current URI for this page, for reference purposes)
Urquhart, J.S.: https://orcid.org/0000-0002-1605-8050
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