PHANGS-JWST First Results: A Global and Moderately Resolved View of Mid-infrared and CO Line Emission from Galaxies at the Start of the JWST Era

Leroy, AK, Bolatto, AD, Sandstrom, K, Rosolowsky, E, Barnes, AT, Bigiel, F, Boquien, M, den Brok, JS, Cao, Y, Chastenet, J, Chevance, M, Chiang, ID, Chown, R, Colombo, D, Ellison, SL, Emsellem, E, Grasha, K, Henshaw, JD ORCID: 0000-0001-9656-7682, Hughes, A, Klessen, RS et al (2023) PHANGS-JWST First Results: A Global and Moderately Resolved View of Mid-infrared and CO Line Emission from Galaxies at the Start of the JWST Era. Astrophysical Journal Letters, 944 (2). ISSN 2041-8205

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Abstract

We explore the relationship between mid-infrared (mid-IR) and CO rotational line emission from massive star-forming galaxies, which is one of the tightest scalings in the local universe. We assemble a large set of unresolved and moderately (∼1 kpc) spatially resolved measurements of CO (1-0) and CO (2-1) intensity, I CO, and mid-IR intensity, I MIR, at 8, 12, 22, and 24 μm. The I CO versus I MIR relationship is reasonably described by a power law with slopes 0.7-1.2 and normalization I CO ∼ 1 K km s−1 at I MIR ∼ 1 MJy sr−1. Both the slopes and intercepts vary systematically with choice of line and band. The comparison between the relations measured for CO (1-0) and CO (2-1) allow us to infer that R 21 ∝ I MIR 0.2 , in good agreement with other work. The 8 μm and 12 μm bands, with strong polycyclic aromatic hydrocarbon (PAH) features, show steeper CO versus mid-IR slopes than the 22 and 24 μm, consistent with PAH emission arising not just from CO-bright gas but also from atomic or CO-dark gas. The CO-to-mid-IR ratio correlates with global galaxy stellar mass (M ⋆) and anticorrelates with star formation rate/M ⋆. At ∼1 kpc resolution, the first four PHANGS-JWST targets show CO-to-mid-IR relationships that are quantitatively similar to our larger literature sample, including showing the steep CO-to-mid-IR slopes for the JWST PAH-tracing bands, although we caution that these initial data have a small sample size and span a limited range of intensities.

Item Type:	Article
Uncontrolled Keywords:	0201 Astronomical and Space Sciences; Astronomy & Astrophysics
Subjects:	Q Science > QB Astronomy Q Science > QC Physics
Divisions:	Astrophysics Research Institute
Publisher:	American Astronomical Society
Date of acceptance:	12 December 2022
Date of first compliant Open Access:	25 September 2024
Date Deposited:	25 Sep 2024 16:07
Last Modified:	04 Jul 2025 08:30
DOI or ID number:	10.3847/2041-8213/acab01
URI:	https://researchonline.ljmu.ac.uk/id/eprint/24277

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