| Title: |
PHANGS–JWST First Results: Mid-infrared Emission Traces Both Gas Column Density and Heating at 100 pc Scales |
| Authors: |
Leroy, AK; Sandstrom, K; Rosolowsky, E; Belfiore, F; Bolatto, AD; Cao, Y; Koch, EW; Schinnerer, E; Barnes, AT; Bešlić, I; Bigiel, F; Blanc, GA; Chastenet, J; Chen, NM; Chevance, M; Chown, R; Congiu, E; Dale, DA; Egorov, OV; Emsellem, E; Eibensteiner, C; Faesi, CM; Glover, SCO; Grasha, K; Groves, B; Hassani, H; Henshaw, JD; Hughes, A; Jiménez-Donaire, MJ; Kim, J; Klessen, RS; Kreckel, K; Kruijssen, JMD; Larson, KL; Lee, JC; Levy, RC; Liu, D; Lopez, LA; Meidt, SE; Murphy, EJ; Neumann, J; Pessa, I; Pety, J; Saito, T; Sardone, A; Sun, J; Thilker, DA; Usero, A; Watkins, EJ; Whitcomb, CM; Williams, TG |
| Publisher Information: |
American Astronomical Society |
| Publication Year: |
2026 |
| Collection: |
Oxford University Research Archive (ORA) |
| Description: |
We compare mid-infrared (mid-IR), extinction-corrected Hα, and CO (2-1) emission at 70-160 pc resolution in the first four PHANGS-JWST targets. We report correlation strengths, intensity ratios, and power-law fits relating emission in JWST’s F770W, F1000W, F1130W, and F2100W bands to CO and Hα. At these scales, CO and Hα each correlate strongly with mid-IR emission, and these correlations are each stronger than the one relating CO to Hα emission. This reflects that mid-IR emission simultaneously acts as a dust column density tracer, leading to a good match with the molecular-gas-tracing CO, and as a heating tracer, leading to a good match with the Hα. By combining mid-IR, CO, and Hα at scales where the overall correlation between cold gas and star formation begins to break down, we are able to separate these two effects. We model the mid-IR above I ν = 0.5 MJy sr−1 at F770W, a cut designed to select regions where the molecular gas dominates the interstellar medium (ISM) mass. This bright emission can be described to first order by a model that combines a CO-tracing component and an Hα-tracing component. The best-fitting models imply that ∼50% of the mid-IR flux arises from molecular gas heated by the diffuse interstellar radiation field, with the remaining ∼50% associated with bright, dusty star-forming regions. We discuss differences between the F770W, F1000W, and F1130W bands and the continuum-dominated F2100W band and suggest next steps for using the mid-IR as an ISM tracer |
| Document Type: |
article in journal/newspaper |
| Language: |
English |
| DOI: |
10.3847/2041-8213/acaf85 |
| Availability: |
https://doi.org/10.3847/2041-8213/acaf85; https://ora.ox.ac.uk/objects/uuid:18d8eb22-73c1-4a49-920e-0e8d549f78e9 |
| Rights: |
info:eu-repo/semantics/openAccess ; CC Attribution (CC BY) |
| Accession Number: |
edsbas.520D021C |
| Database: |
BASE |