Open AccessRefined molecular gas mass and star‐formation efficiency in NGC 3627
Author(s) -
Watanabe Y.,
Sorai K.,
Kuno N.,
Habe A.
Publication year - 2011
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2010.17746.x
Subject(s) - physics , astrophysics , bar (unit) , galaxy , star formation , spiral galaxy , telescope , intensity (physics) , star (game theory) , gravitational potential , mean kinetic temperature , barred spiral galaxy , galaxy merger , optics , meteorology
We present a 13 CO ( 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 13 CO ( J = 1–0) morphology of NGC 3627 is similar to the 12 CO ( J = 1–0) map and the 12 CO ( J = 1–0) / 13 CO ( 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 12 CO ( 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 13 CO ( 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.