1999/06/30 by Jonathan C. Tan · 2 citations
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Galaxy #Milky Way #Molecular cloud #Physics #Spiral galaxy #Star formation #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/308905
27 pages including 3 figures and 2 tables. Accepted to ApJ. Expanded statistical analysis of cloud SF efficiency test. Stylistic changes. Data for figures available electronically at http://astro.berkeley.edu/~jt/disksfr.html
arxiv created 2000/01/24 · openalex publication_date 2000/06/10 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We invoke star formation triggered by cloud-cloud collisions to explain global star formation rates of disk galaxies and circumnuclear starbursts. Previous theories based on the growth rate of gravitational perturbations ignore the dynamically important presence of magnetic fields. Theories based on triggering by spiral density waves fail to explain star formation in systems without such waves. Furthermore, observations suggest gas and stellar disk instabilities are decoupled. Following Gammie, Ostriker, & Jog, the cloud collision rate is set by the shear velocity of encounters with initial impact parameters of a few tidal radii, due to differential rotation in the disk. This, together with the effective confinement of cloud orbits to a two-dimensional plane, enhances the collision rate above that for particles in a three-dimensional box. We predict Σ SFR ( R ) ∝ Σ gas Ω(1 - 0.7β). For constant circular velocity (β = 0), this is in agreement with recent observations by Kennicutt. Our estimates for the normalization of this star formation law, while uncertain, are consistent with the observed star formation in the Milky Way and starburst galaxies. We predict a B -band Tully-Fisher relation: L B ∝ v , also consistent with observations. As additional tests, we predict enhanced/reduced star formation in regions with relatively high/low shear rates, and lower star formation efficiencies in clouds of higher mass.