Jiayi Sun

Team Member Profile: Jiayi Sun

Position: NASA Hubble Fellow at Princeton University

Professional webpage: https://astrojysun.github.io

General science interest: I study the interstellar medium (ISM) in the broad contexts of star formation and galaxy evolution. With multiwavelength observations, I aim to understand how stars and star clusters form out of the ISM in galaxies, how stellar feedback ends this process and reshapes the ISM, and how galactic and circumgalactic environments influence the ISM and subsequently change the course of galaxy evolution.

My role in PHANGS: With the PHANGS-ALMA CO data, I extracted more than 100,000 independent measurements of molecular gas properties on 50-150 parsec scales across the local star-forming galaxy population (Sun et PHANGS 2018; Sun et PHANGS 2020b). I further assembled a multiwavelength database that synthesized measurements from ALMA, VLA, VLT, HST, and other telescopes, thereby providing a full inventory of gas and stellar mass distributions, kinematics, morphological structures, and star formation activities (Sun et PHANGS 2022). With this rich database, I showed that molecular cloud characteristics correlate strongly with the local and global host galaxy properties (Sun et PHANGS 2020b, 2022); I also quantified the characteristic timescales of cloud evolution, gas depletion, and the star formation efficiencies they imply (Utomo, Sun, et PHANGS 2018, Sun et PHANGS 2022, 2023). The same database has also supported, and will continue to support, a wide range of PHANGS projects on the multi-phase ISM and gas outflows, galaxy disk structures and instabilities, among other topics (Herrera et PHANGS 2020; Barnes et PHANGS 2021; Querejeta et PHANGS 2021; Stuber et PHANGS 2021; Zakardjian et PHANGS 2023; Meidt et PHANGS in prep.; Williams et PHANGS in prep.).

I am now leading an ambitious ALMA program (400+ hours total; 35 hours on the 12-m array) to conduct high-resolution CO mapping for a large sample of galaxies in the Virgo Cluster. This program will reveal how environmental processes external to a galaxy (on Mpc scale) can influence the ISM structures within it (down to cloud scales) and subsequently enhance or suppress star formation. Furthermore, together with many collaborators in PHANGS, we are building a new generation of PHANGS surveys on JWST, ALMA, and other facilities. These surveys are pushing the frontier of extragalactic ISM and star / cluster formation studies all the way to 1-10 pc scales.

This figure demonstrates how molecular gas properties on 120 parsec scales vary within and across galaxies (see Sun, J. and the PHANGS Collaboration, 2018). The spread in molecular gas surface density and velocity dispersion (top), dynamical state (bottom left), and turbulent pressure (bottom right) is evident across the 15 nearby galaxies examined. There is also a clear contrast between normal star-forming galaxies (blue, including 11 PHANGS-ALMA targets), a merger system (orange), and two more quiescent galaxies (green).

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