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Molecular Cloud Populations In The Context Of Their Galactic Environments: Insights From PHANGS-ALMA

Presentation #310.04 in the session “Extragalactic Interstellar Medium: PHANGS”.

Published onJun 18, 2021
Molecular Cloud Populations In The Context Of Their Galactic Environments: Insights From PHANGS-ALMA

The physical properties of molecular clouds relate closely to their ability to form stars and the output stellar population. Therefore, understanding the environmental dependence of molecular cloud properties is fundamental to understanding galaxy evolution. We present a joint analysis of the molecular cloud population statistics and local galactic environmental properties in ~80 nearby galaxies covered by the PHANGS-ALMA project. We derive key molecular cloud properties (e.g., mass, surface density, and virial parameter) from PHANGS-ALMA CO(2-1) data and associated CPROPS molecular cloud catalogs, and further investigate their empirical correlations with normalized galactocentric radii, local shear and rotation speed, as well as kpc-scale gas and stellar mass surface densities. We find that most molecular cloud characteristics depend primarily on the local molecular or total gas surface densities, and several of them (including mass and surface density) also show clear secondary dependence on stellar surface density and/or galactic orbital properties. Finally, we provide estimates of several timescales relevant to molecular cloud formation and evolution. From the shortest to the longest, these timescales are: free-fall time, turbulent crossing time, shearing and orbital timescales, cloud-cloud collision timescale, and molecular gas depletion time.


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