My Research


My research focuses on characterizing and understanding the physical properties of molecular clouds in nearby galaxies. My PhD thesis work uses high-resolution ALMA observations from the PHANGS-ALMA survey to construct by far the largest homogeneous dataset of molecular cloud measurements across the local galaxy population. Pairing this unprecedented dataset with multiwavelength observations from ground- and space-based telescopes (e.g., VLA, VLT, HST), I put molecular clouds into the context of their galactic environment and unveil how their properties are related to star formation, stellar feedback, and dynamical processes.

Mapping Molecular Clouds across the Local Star-forming Galaxy Population

I am leading the efforts on measuring fundamental properties of molecular clouds in an unprecedented sample of nearby galaxies, using the PHANGS-ALMA CO(2-1) imaging data. This new dataset provides by far the best synthetic view of molecular cloud properties across the local star-forming galaxy population. My paper in 2018 presented a thorough analysis of ~30,000 molecular cloud measurements across 15 galaxies. My second paper in 2020 further extended this analysis to ~100,000 molecular cloud measurements across 70 galaxies.

Sun et al. (2018): [ADS, video, data table, slides]
Sun et al. (2020b): [ADS, data tables, slides]

Putting Molecular Clouds in the Context of Their Natal Environment

Based on a joint analysis of the PHANGS-ALMA CO dataset and multiwavelength supporting data, I found strong evidence that molecular clouds were connected to their natal environment in the host galaxy. My first paper in 2020 showed that the molecular cloud populations in star-forming galaxy disks would conform to a dynamical equilibrium state set by the interplay between gas pressures and gravitational forces. This study highlighted several key mechanisms that shaped the properties of molecular clouds and regulated star formation in local star-forming galaxies.

Sun et al. (2020a): [ADS, video, data tables, slides]

Fig. 2 in Utomo et al. (2018)

Measuring Star Formation Efficiency in the Molecular ISM in Galaxies

In 2018, my colleague Dyas Utomo and I led a synthetic work that quantified the (in)efficiency of star formation in the molecular ISM in 14 nearby galaxies. Across this sample, we estimated a median value of 0.7% for the star formation efficiency per free-fall time --- a key dimensionless parameter widely used in star formation simulations and analytic models. We are currently expanding this analysis to the full PHANGS-ALMA galaxy sample and testing theoretical models of star formation in molecular clouds.

Fig. 1 in Dobbs et al. (2019)

Connecting Observations with Numerical Simulations

In 2019, I performed a proof-of-concept experiment as part of a project comparing observations of the nearby galaxy M33 to "bespoke" numerical simulations. We showed that molecular cloud properties were primarily set by the gas and stellar mass distribution in the host galaxy, and that the simulations could reproduce the observations well. In close collaboration with numerical simulators, I am now conducting similar experiments on simulations covering a wider range of galactic environments.


ADS Library ORCiD Google Scholar

Contact me

Email: sun208@mcmaster.ca
Address: 1280 Main Street West
Hamilton, Ontario L8S 4L8.


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