CO Multi-line Imaging of Nearby Galaxies (COMING). III. Dynamical effect on molecular gas density and star formation in the barred spiral galaxy NGC 4303

Yoshiyuki Yajima, Kazuo Sorai, Nario Kuno, Kazuyuki Muraoka, Yusuke Miyamoto, Hiroyuki Kaneko, Hiroyuki Nakanishi, Naomasa Nakai, Takahiro Tanaka, Yuya Sato, Dragan Salak, Kana Morokuma-Matsui, Naoko Matsumoto, Hsi An Pan, Yuto Noma, Tsutomu T. Takeuchi, Moe Yoda, Mayu Kuroda, Atsushi Yasuda, Nagisa OiShugo Shibata, Masumichi Seta, Yoshimasa Watanabe, Shoichiro Kita, Ryusei Komatsuzaki, Ayumi Kajikawa, Yu Yashima

Research output: Contribution to journalArticlepeer-review

4 Citations (Scopus)

Abstract

We present the results of $^{12}\textrm{C}$$\textrm{O}$(J = 1-0) and $^{13}\textrm{C}$$\textrm{O}$(J = 1-0) simultaneous mappings toward the nearby barred spiral galaxy NGC 4303 as part of the CO Multi-line Imaging of Nearby Galaxies (COMING) project. Barred spiral galaxies often show lower star-formation efficiency (SFE) in their bar region compared to the spiral arms. In this paper, we examine the relation between the SFEs and the volume densities of molecular gas n(H2) in the eight different regions within the galactic disk with $\textrm{C}$$\textrm{O}$ data combined with archival far-ultraviolet and 24 μm data. We confirmed that SFE in the bar region is lower by 39% than that in the spiral arms. Moreover, velocity-alignment stacking analysis was performed for the spectra in the individual regions. Integrated intensity ratios of $^{12}\textrm{C}$$\textrm{O}$ to $^{13}\textrm{C}$$\textrm{O}$ (R12/13) ranging from 10 to 17 were the results of this stacking. Fixing a kinetic temperature of molecular gas, $n(\rm {H_2})$ was derived from R12/13 via non-local thermodynamic equilibrium (non-LTE) analysis. The density n(H2) in the bar is lower by 31%-37% than that in the arms and there is a rather tight positive correlation between SFEs and n(H2), with a correlation coefficient of ∼0.8. Furthermore, we found a dependence of $n(\rm {H}_2)$ on the velocity dispersion of inter-molecular clouds (ΔV/sin i). Specifically, n(H2) increases as ΔV/sin i increases when ΔV/sin i < 100 km s-1. On the other hand, n(H2) decreases as ΔV/sin i increases when ΔV/sin i > 100 km s-1. These relations indicate that the variations of SFE could be caused by the volume densities of molecular gas, and the volume densities could be governed by the dynamical influence such as cloud-cloud collisions, shear, and enhanced inner-cloud turbulence.

Original languageEnglish
Article numberS13
JournalPublications of the Astronomical Society of Japan
Volume71
DOIs
Publication statusPublished - 2019 Dec 1
Externally publishedYes

Keywords

  • Galaxies: individual (NGC 4303)
  • Galaxies: ISM
  • Galaxies: spiral
  • Galaxies: star formation
  • Radio lines: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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