Cloud-scale Molecular Gas Properties in 15 Nearby Galaxies

By Jiayi Sun, A. Leroy, A. Schruba, Erik Rosolowsky, Annie Hughes, J. Kruijssen, S. Meidt, E. Schinnerer, G. Blanc, F. Bigiel and 9 more. Astrophysical Journal, 2018

165 citations recorded by the source corpus.

We measure the velocity dispersion, σ, and surface density, Σ, of the molecular gas in nearby galaxies from CO spectral line cubes with spatial resolution 45–120 pc, matched to the size of individual giant molecular clouds. Combining 11 galaxies from the PHANGS-ALMA survey with four targets from the literature, we characterize ∼30,000 independent sightlines where CO is detected at good significance. Σ and σ show a strong positive correlation, with the best-fit power-law slope close to the expected value for resolved, self-gravitating clouds. This indicates only a weak variation in the virial parameter αvir ∝ σ2/Σ, which is ∼1.5–3.0 for most galaxies. We do, however, observe enormous variation in the internal turbulent pressure Pturb ∝ Σσ2, which spans ∼5 dex across our sample. We find Σ, σ, and Pturb to be systematically larger in more massive galaxies. The same quantities appear enhanced in the central kiloparsec of strongly barred galaxies relative to their disks. Based on sensitive maps of M31 and M33, the slope of the σ–Σ relation flattens at Σ ≲ 10 M⊙ pc−2, leading to high σ for a given Σ and high apparent αvir. This echoes results found in the Milky Way and likely originates from a combination of lower beam-filling factors and a stronger influence of local environment on the dynamical state of molecular gas in the low-density regime.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/77fb421a5436c98bba78e8f570e473df6dfd216f

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In Astronomy and Astrophysics

1. A. Leroy
2. Mark R. Krumholz
3. S. Glover
4. D. Kruijssen
5. S. Longmore
6. A. Schruba
7. A. Usero
8. E. Schinnerer

In Instrumentation

1. A. Leroy
2. S. Longmore
3. Erik Rosolowsky
4. A. Schruba
5. S. Glover
6. E. Schinnerer
7. Annie Hughes
8. S. Meidt

Citations in the corpus

• The lifecycle of molecular clouds in nearby star-forming disc galaxies (2019, background): “These maps recover most of the CO emission present in the data cube, including low signal-to-noise flux, resulting in high completeness (Sun et al. 2018), but also higher noise compared to maps using more restrictive masking of the faint CO emission.”