PHANGS-JWST First Results: The Dust Filament Network of NGC 628 and its Relation to Star Formation Activity

TL;DR

This study maps and analyzes the dust filament network in NGC 628 using JWST and HST imaging, revealing its spatial relationship with star-forming regions and its potential role in star formation processes.

Contribution

It provides the first detailed, multi-scale mapping of the dust filament network in NGC 628, linking MIR emission, dust attenuation, and star formation activity.

Findings

40% of sight lines show co-spatial filaments in emission and attenuation.

Approximately 30% of MIR flux is in the dust filament network.

75-80% of young HII regions are within the dust filament network.

Abstract

PHANGS-JWST mid-infrared (MIR) imaging of nearby spiral galaxies has revealed ubiquitous filaments of dust emission in intricate detail. We present a pilot study to systematically map the dust filament network (DFN) at multiple scales between 25-400 pc in NGC 628. MIRI images at 7.7, 10, 11.3 and 21$\mu$m of NGC 628 are used to generate maps of the filaments in emission, while PHANGS-HST B-band imaging yields maps of dust attenuation features. We quantify the correspondence between filaments traced by MIR thermal continuum / polycyclic aromatic hydrocarbon (PAH) emission and filaments detected via extinction / scattering of visible light; the fraction of MIR flux contained in the DFN; and the fraction of HII regions, young star clusters and associations within the DFN. We examine the dependence of these quantities with the physical scale at which the DFN is extracted. With our highest resolution DFN maps (25 pc filament width), we find that filaments in emission and attenuation are co-spatial in 40% of sight lines, often exhibiting detailed morphological agreement; that ~30% of the MIR flux is associated with the DFN; and that 75-80% of HII regions and 60% of star clusters younger than 5 Myr are contained within the DFN. However, the DFN at this scale is anti-correlated with looser associations of stars younger than 5 Myr identified using PHANGS-HST near-UV imaging. We discuss the impact of these findings for studies of star formation and the ISM, and the broad range of new investigations enabled with multi-scale maps of the DFN.