Journal Article

Refined molecular gas mass and star-formation efficiency in NGC 3627

Y. Watanabe, K. Sorai, N. Kuno and A. Habe

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 411, issue 3, pages 1409-1417
Published in print March 2011 | ISSN: 0035-8711
Published online February 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17746.x
Refined molecular gas mass and star-formation efficiency in NGC 3627

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We present a 13CO (J= 1–0) mapping observation of the nearby barred spiral galaxy NGC 3627, covering almost all the stellar disc, with the Nobeyama 45-m telescope. We found that the 13CO (J= 1–0) morphology of NGC 3627 is similar to the 12CO (J= 1–0) map and the 12CO (J= 1–0)/13CO (J= 1–0) intensity ratio is 10.7 ± 0.4 on average. We also found that the ratio varies position-to-position in the galaxy and decreases with the galactocentric distance. The ratio is especially high, ∼20, in the bar and this result suggests that the molecular gas mass calculated from the 12CO (J= 1–0) intensity with constant conversion factor is overestimated in the bar. As a result, the star-formation efficiency (SFE) in the bar, which is derived from 13CO (J= 1–0) intensity, is similar to that in the other regions except for the two bar ends and the centre. We found that the SFE is higher in the bar ends than in the other regions. We discuss plausible reasons for the enhanced SFE in the bar: the kinetic temperature of the molecular gas, the spatial gap between the molecular gas peak and star formation and gravitational instability.

Keywords: galaxies: individual: NGC 3627; galaxies: ISM; galaxies: spiral; radio lines: galaxies

Journal Article.  6120 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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