CO Multi-line Imaging of Nearby Galaxies (COMING). VI. Radial variations in star formation efficiency
| Autor: | Hsi-An Pan, Atsushi Yasuda, Mayu Kuroda, Moe Yoda, Tsutomu T. Takeuchi, Yoshiyuki Yajima, Kana Morokuma-Matsui, Ayumi Kajikawa, Masato I. N. Kobayashi, Daniel Espada, Ryusei Komatsuzaki, Nario Kuno, Hiroyuki Nakanishi, Yusuke Miyamoto, Yuto Noma, Takahiro Tanaka, Naomasa Nakai, Kazuyuki Muraoka, Nagisa Oi, Naoko Matsumoto, Dragan Salak, Yu Yashima, Kazuo Sorai, Masumichi Seta, Shugo Shibata, Yoshimasa Watanabe, Shoichiro Kita, Hiroyuki Kaneko |
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| Rok vydání: | 2019 |
| Předmět: |
Physics
Spiral galaxy Initial mass function Stellar mass 010308 nuclear & particles physics Star formation Metallicity FOS: Physical sciences Astronomy and Astrophysics Radius Astrophysics Astrophysics - Astrophysics of Galaxies 01 natural sciences Galaxy Space and Planetary Science Astrophysics of Galaxies (astro-ph.GA) 0103 physical sciences 010303 astronomy & astrophysics Line (formation) |
| Zdroj: | Publications of the Astronomical Society of Japan. 71 |
| ISSN: | 2053-051X 0004-6264 |
| DOI: | 10.1093/pasj/psz015 |
| Popis: | We examined radial variations in molecular-gas based star formation efficiency (SFE), which is defined as star formation rate per unit molecular gas mass, for 80 galaxies selected from the CO Multi-line Imaging of Nearby Galaxies project (Sorai et al. 2019). The radial variations in SFE for individual galaxies are typically a factor of 2 -- 3, which suggests that SFE is nearly constant along galactocentric radius. We found the averaged SFE in 80 galaxies of $(1.69 \pm 1.1) \times 10^{-9}$ yr$^{-1}$, which is consistent with Leroy et al. 2008 if we consider the contribution of helium to the molecular gas mass evaluation and the difference in the assumed initial mass function between two studies. We compared SFE among different morphological (i.e., SA, SAB, and SB) types, and found that SFE within the inner radii ($r/r_{25} < 0.3$, where $r_{25}$ is $B$-band isophotal radius at 25 mag arcsec$^{-2}$) of SB galaxies is slightly higher than that of SA and SAB galaxies. This trend can be partly explained by the dependence of SFE on global stellar mass, which probably relates to the CO-to-H$_2$ conversion factor through the metallicity. For two representative SB galaxies in our sample, NGC 3367 and NGC 7479, the ellipse of $r/r_{25}$ = 0.3 seems to cover not only the central region but also the inner part of the disk, mainly the bar. These two galaxies show higher SFE in the bar than in spiral arms. However, we found an opposite trend in NGC 4303; SFE is lower in the bar than in spiral arms, which is consistent with earlier studies (e.g., Momose et al. 2010). These results suggest diversity of star formation activities in the bar. 28 pages, 12 figures, accepted for publication in PASJ |
| Databáze: | OpenAIRE |
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