My Research


My research focuses on understanding the physics of the interstellar medium (ISM) in the broad context of star formation and galaxy evolution. Leading observational efforts in the PHANGS collaboration, I synthesize robust measurements for the largest homogeneous sample of molecular clouds to date, quantify their star formation efficiencies and evolutionary timescales, delineate their dependence on host galaxy properties, and identify key physical drivers of such dependence. I also work closely with theorists on testing analytical and numerical models of star formation on the scales of both individual star forming regions and whole galaxies.

PHANGS-ALMA CO data

Mapping Molecular Clouds across the Local Star-forming Galaxy Population

I lead the efforts on characterizing 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 the molecular cloud populations inhabiting star-forming galaxies in the present-day universe. 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. (2020b): [ADS, data tables, slides]
Sun et al. (2018): [ADS, video, data table, slides]

A multiwavelength view of NGC 628

Putting Molecular Clouds, HII regions, and Star Clusters in a Galactic Context

I am leading the construction and continuous improvement of a multiwavelength database, which leverages the full set of PHANGS surveys with cutting-edge facilities (including ALMA, VLT/MUSE, HST, and JWST). It synthesizes high-resolution measurements for molecular clouds, HII regions, and star clusters, as well as ancillary information about the host galaxies. My first paper in 2020 used this database to show that the average pressure in the ISM plays a major role in shaping the internal dynamics of molecular clouds and determining star formation rate in disk galaxies.

Sun et al. (2022): [ADS, data tables, slides]
Sun et al. (2020a): [ADS, video, data tables, slides]

Fig. 3 in Sun et al. (2023)

Quantifying the Efficiencies of Star Formation and Stellar Feedback

I actively work on measuring robust star formation rates and efficiencies and quantifying their dependence on ISM properties. In a 2018 paper, my colleague and I found that the star formation efficiency per free-fall time — a key dimensionless parameter in numerical and analytic models — is about 0.7% across 14 nearby galaxies. My paper in 2023 substantially expands this analysis by determining the molecular gas depletion time, the star formation efficiency per free-fall time and per orbital time, and the feedback yield over the full PHANGS galaxy sample.

Sun et al. (2023): [ADS, data tables, slides]
Utomo, Sun, et al. (2018): [ADS]

Fig. 1 in Dobbs et al. (2019)

Connecting Observations with Numerical Simulations

I also work closely with researchers running numerical simulations over a broad range of spatial scales. In a 2019 paper, I conducted a proof-of-concept experiment in a collaborative project that compares the observed molecular clouds in M33 to those in a set of dedicated simulations. In a 2022 paper, my colleagues and I proposed a novel method for estimating the (unobservable) molecular disk vertical scale height in face-on galaxies and tested it in a galaxy-scale simulation. I am now working on extending these efforts to observations and simulations probing more extreme conditions, especially high gas density and pressure, in order to provide more stringent constraints on physical models of star formation, stellar feedback, and chemical network.

Jeffreson, Sun, & Wilson (2022): [ADS]


ADS Library ORCiD Google Scholar

Contact me

Email: jiayi.sun@princeton.edu
Address: 110A Peyton Hall
4 Ivy Ln, Princeton, NJ 08544


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