PHANGS--JWST First Results: ISM structure on the turbulent Jeans scale in four disk galaxies observed by JWST and ALMA

TL;DR

This study uses JWST and ALMA observations to analyze the multi-scale gas structures in four nearby disk galaxies, finding that Jeans-scale structures are common and likely related to gravitational instability, influencing star formation.

Contribution

It provides the first detailed comparison of observed gas structures with theoretical instability scales across multiple galaxies using JWST and ALMA data.

Findings

Jeans-scale structures are prevalent in all four galaxies.

Filamentary features are consistent with gravitational fragmentation.

The observed structures influence star formation processes.

Abstract

JWST/MIRI imaging of the nearby galaxies IC 5332, NGC 628, NGC 1365 and NGC 7496 from PHANGS reveals a richness of gas structures that in each case form a quasi-regular network of interconnected filaments, shells and voids. We examine whether this multi-scale network of structure is consistent with the fragmentation of the gas disk through gravitational instability. We use FilFinder to detect the web of filamentary features in each galaxy and determine their characteristic radial and azimuthal spacings. These spacings are then compared to estimates of the most Toomre-unstable length (a few kpc), the turbulent Jeans length (a few hundred pc) and the disk scale height (tens of pc) reconstructed using PHANGS-ALMA observations of the molecular gas as a dynamical tracer. Our analysis of the four galaxies targeted in this work indicates that Jeans-scale structure is pervasive. Future work will be essential for determining how the structure observed in gas disks impacts not only the rate and location of star formation but also how stellar feedback interacts positively or negatively with the surrounding multi-phase gas reservoir.