Journal Article

The effect of spiral arms on star formation in the Galaxy

T. J. T. Moore, J. S. Urquhart, L. K. Morgan and M. A. Thompson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 426, issue 1, pages 701-707
Published in print October 2012 | ISSN: 0035-8711
Published online October 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21740.x
The effect of spiral arms on star formation in the Galaxy

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Abstract

We have examined the ratio between the integrated luminosity of massive young stellar objects detected by the Red MSX Source (RMS) survey and the mass of molecular clouds in the Galactic Ring Survey (GRS) region, as a function of Galactocentric radius. The results indicate that 60–80 per cent of the observed increases in the star formation rate density associated with spiral-arm features are due to source crowding within the arms. Of the remainder, most of the increase in the inner Sagittarius arm is due to an enhancement in the simple star formation efficiency, i.e. in the number of RMS sources per unit molecular gas mass. In the inner Perseus arm, the residual increase is due to a higher than average mean source luminosity, which implies a top-heavy initial mass function, and this is entirely due to the presence, in the GRS region, of the W49 star-forming complex, which appears to be exceptional in its nature. The results also suggest that there is little or no increase in the star formation efficiency on kiloparsec scales in the Scutum tangent region which includes W43. We discuss the possible role played by the spiral arms in influencing the star formation efficiency and conclude that the most likely mechanisms are related to orbit crowding within the arms.

Keywords: stars: formation; ISM: clouds; Galaxy: structure

Journal Article.  5226 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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