Threshold between Spontaneous and Cloud-Collisional Star Formation

Abstract

Based on simple physical and geometric assumptions, we have calculated the mean surface molecular density of spiral galaxies at the threshold between star formation induced by cloud-cloud collision and spontaneous gravitational collapse. The calculated threshold is approximately $\log {\Sigma }_{\mathrm{crit}}\sim 2.5$, where $ Σ\quad \mathrm{M_{\solar}}\cdot \mathrm{pc}^{-2}$ is the observed surface mass density of an assumed flat gas disk. Above this limit, the rate of molecular cloud collisions dominates over spontaneous molecular cloud collapse. This model may explain the apparent discontinuity in the Schmidt law found recently at $2\lesssim \log \Sigma \lesssim 3$.

Accepted for publication in PASJ

References in corpus (1)

• The Virgo CO Survey: VI. Gas Dynamics and Star Formation Along the Bar in NGC 4303

Cited by in corpus (5)

• The Star Formation Law in Atomic and Molecular Gas
• CO Multi-line Imaging of Nearby Galaxies (COMING). IX. ${}^{12}$CO($J$=2-1)/${}^{12}$CO($J$=1-0) line ratio on kiloparsec scales
• Deep CO Observations and the CO-to-H_2 Conversion Factor in DDO 154, a Low Metallicity Dwarf Irregular Galaxy
• Radial Variations of the Volume- and Surface-Star Formation Laws in the Galaxy
• Star Formation Law in the Milky Way