Revealing the Connection between the Filamentary Hierarchy and Star Cluster Formation in a Simulated NGC 628 Galaxy

There is abundant observational evidence for the hierarchical, interconnected nature of filaments in the interstellar medium extending from galactic down to subparsec scales. New JWST images of NGC 628, in particular, show clusters forming along the two spiral arms of this galaxy. In this paper, we investigate filament and cluster properties in an NGC 628-like multiscale high-resolution magnetohydrodynamic simulation. We use a filament finding tool to identify filaments and derive the probability density functions (PDFs) for the filament lengths and masses. Using a clustering algorithm, we identify star clusters formed between 268 and 278 Myr and follow this population as the galaxy evolves for 60 Myr, calculating their mass PDFs, average radius growth rate, and average mass loss rate. We find a power-law index of αm = −1.35 for the filament masses. Calculating the power-law index from our cluster mass PDF, we find a value of αc,m = −1.35 when the clusters first form, exactly our filament mass power-law index. This shows that properties of young clusters arise from the gravitational fragmentation of their host filaments. We track the postformation evolution of the clusters as they become unbound, increase in radius, and decrease in mass, yielding an ever steeper mass power-law index. After 60 Myr, the mass power-law index is αc,m = −1.55, matching other simulations and observations.