Molecular Cloud Populations in the Context of Their Host Galaxy Environments: A Multiwavelength Perspective
Creators: name: Sun, Jiayi
name: Leroy, Adam K.
name: Rosolowsky, Erik
name: Hughes, Annie
name: Schinnerer, Eva
name: Schruba, Andreas
name: Koch, Eric W.
name: Blanc, Guillermo A.
name: Chiang, I-Da
name: Groves, Brent
name: Liu, Daizhong
name: Meidt, Sharon
name: Pan, Hsi-An
name: Pety, Jerome
name: Querejeta, Miguel
name: Saito, Toshiki
name: Sandstrom, Karin
name: Sardone, Amy
name: Usero, Antonio
name: Utomo, Dyas
name: Williams, Thomas G.
name: Barnes, Ashley T.
name: Benincasa, Samantha M.
name: Bigiel, Frank
name: Bolatto, Alberto D.
name: Boquien, Mederic
name: Chevance, Melanie
name: Dale, Daniel A.
name: Deger, Sinan
name: Emsellem, Eric
name: Glover, Simon C. O.
name: Grasha, Kathryn
name: Henshaw, Jonathan D.
name: Klessen, Ralf S.
name: Kreckel, Kathryn
name: Kruijssen, J. M. Diederik
name: Ostriker, Eve C.
name: Thilker, David A.
Publisher: name: arXiv
Year: 2022
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present a rich, multiwavelength, multiscale database built around the PHANGS-ALMA CO$\,$(2-1) survey and ancillary data. We use this database to present the distributions of molecular cloud populations and sub-galactic environments in 80 PHANGS galaxies, to characterize the relationship between population-averaged cloud properties and host galaxy properties, and to assess key timescales relevant to molecular cloud evolution and star formation. We show that PHANGS probes a wide range of kpc-scale gas, stellar, and star formation rate (SFR) surface densities, as well as orbital velocities and shear. The population-averaged cloud properties in each aperture correlate strongly with both local environmental properties and host galaxy global properties. Leveraging a variable selection analysis, we find that the kpc-scale surface densities of molecular gas and SFR tend to possess the most predictive power for the population-averaged cloud properties. Once their variations are controlled for, galaxy global properties contain little additional information, which implies that the apparent galaxy-to-galaxy variations in cloud populations are likely mediated by kpc-scale environmental conditions. We further estimate a suite of important timescales from our multiwavelength measurements. The cloud-scale free-fall time and turbulence crossing time are ${\sim}5{-}20$ Myr, comparable to previous cloud lifetime estimates. The timescales for orbital motion, shearing, and cloud-cloud collisions are longer, ${\sim}100$ Myr. The molecular gas depletion time is $1{-}3$ Gyr and shows weak to no correlations with the other timescales in our data. We publish our measurements online and expect them to have broad utility to future studies of molecular clouds and star formation.
description: 32 pages + 6 appendices. AJ in press. Data products available at https://www.canfar.net/storage/list/phangs/RELEASES/Sun_etal_2022 . Associated software package available at https://doi.org/10.5281/zenodo.6584842 . Slides summarizing the key results can be found at https://www.dropbox.com/s/7llnrob9wi0isfk/Sun_et_PHANGS_2022.pptx?dl=0