paper

Dynamical Equilibrium in the Molecular ISM in 28 Nearby Star-Forming Galaxies

arXiv:2002.08964 · doi:10.3847/1538-4357/ab781c

Abstract

We compare the observed turbulent pressure in molecular gas, , to the required pressure for the interstellar gas to stay in equilibrium in the gravitational potential of a galaxy, . To do this, we combine arcsecond resolution CO data from PHANGS-ALMA with multi-wavelength data that traces the atomic gas, stellar structure, and star formation rate (SFR) for 28 nearby star-forming galaxies. We find that correlates with, but almost always exceeds the estimated on kiloparsec scales. This indicates that the molecular gas is over-pressurized relative to the large-scale environment. We show that this over-pressurization can be explained by the clumpy nature of molecular gas; a revised estimate of on cloud scales, which accounts for molecular gas self-gravity, external gravity, and ambient pressure, agrees well with the observed in galaxy disks. We also find that molecular gas with cloud-scale in our sample is more likely to be self-gravitating, whereas gas at lower pressure appears more influenced by ambient pressure and/or external gravity. Furthermore, we show that the ratio between and the observed SFR surface density, , is compatible with stellar feedback-driven momentum injection in most cases, while a subset of the regions may show evidence of turbulence driven by additional sources. The correlation between and kpc-scale in galaxy disks is consistent with the expectation from self-regulated star formation models. Finally, we confirm the empirical correlation between molecular-to-atomic gas ratio and kpc-scale reported in previous works.

arXiv comment28 pages + 3 appendices, ApJ in press. See https://www.youtube.com/watch?v=qxkd-RXB0Ek for a short video describing the main results. Data tables available at https://www.canfar.net/storage/list/phangs/RELEASES/Sun_etal_2020 prior to publication

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