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

Jiayi Sun, Adam K. Leroy, Eve C. Ostriker, Annie Hughes, Erik Rosolowsky, Andreas Schruba, Eva Schinnerer, Guillermo A. Blanc, Christopher Faesi, J. M.Diederik Kruijssen, Sharon Meidt, Dyas Utomo, Frank Bigiel, Alberto D. Bolatto, Mélanie Chevance, I. Da Chiang, Daniel Dale, Eric Emsellem, Simon C.O. Glover, Kathryn GrashaJonathan Henshaw, Cinthya N. Herrera, Maria Jesus Jimenez-Donaire, Janice C. Lee, Jérôme Pety, Miguel Querejeta, Toshiki Saito, Karin Sandstrom, Antonio Usero

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Abstract

We compare the observed turbulent pressure in molecular gas, P turb, to the required pressure for the interstellar gas to stay in equilibrium in the gravitational potential of a galaxy, P DE. To do this, we combine arcsecond resolution CO data from PHANGS-ALMA with multiwavelength data that trace the atomic gas, stellar structure, and star formation rate (SFR) for 28 nearby star-forming galaxies. We find that P turb correlates with-but almost always exceeds-the estimated P DE on kiloparsec scales. This indicates that the molecular gas is overpressurized relative to the large-scale environment. We show that this overpressurization can be explained by the clumpy nature of molecular gas; a revised estimate of P DE on cloud scales, which accounts for molecular gas self-gravity, external gravity, and ambient pressure, agrees well with the observed P turb in galaxy disks. We also find that molecular gas with cloud-scale Pturb ≈ PDE 10 × 5, k_BK cm-3 in our sample is more likely to be self-gravitating, whereas gas at lower pressure it appears more influenced by ambient pressure and/or external gravity. Furthermore, we show that the ratio between P turb and the observed SFR surface density, Σ SFR, 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 Σ SFR and kpc-scale P DE 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 P DE reported in previous works.

Original languageEnglish (US)
Article number148
JournalAstrophysical Journal
Volume892
Issue number2
DOIs
StatePublished - Apr 1 2020

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Sun, J., Leroy, A. K., Ostriker, E. C., Hughes, A., Rosolowsky, E., Schruba, A., Schinnerer, E., Blanc, G. A., Faesi, C., Kruijssen, J. M. D., Meidt, S., Utomo, D., Bigiel, F., Bolatto, A. D., Chevance, M., Chiang, I. D., Dale, D., Emsellem, E., Glover, S. C. O., ... Usero, A. (2020). Dynamical Equilibrium in the Molecular ISM in 28 Nearby Star-forming Galaxies. Astrophysical Journal, 892(2), [148]. https://doi.org/10.3847/1538-4357/ab781c