Cold Gas and Star Formation in the Phoenix Cluster with JWST

Reefe, Michael; Mcdonald, Michael; Chatzikos, Marios; Seebeck, Jerome; Mushotzky, Richard; Veilleux, Sylvain; Allen, Steven W; Bayliss, Matthew; Calzadilla, Michael; Canning, Rebecca; Donahue, Megan; Floyd, Benjamin; Gaspari, Massimo; Hlavacek-Larrondo, Julie; Mcnamara, Brian; Russell, Helen; Sarkar, Arnab; Sharon, Keren; Somboonpanyakul, Taweewat

Abstract

We present integral field unit observations of the Phoenix Cluster with the JWST Mid-infrared Instrument's Medium Resolution Spectrometer (MIRI/MRS). We focus this study on the molecular gas, dust, and star formation in the brightest cluster galaxy (BCG). We use precise spectral modeling to produce maps of the silicate dust, molecular gas, and polycyclic aromatic hydrocarbons (PAHs) in the inner ∼50 kpc of the cluster. We measure the optical depth from silicates by comparing the observed H 2 line ratios to those predicted by excitation models. We provide updated measurements of the total molecular gas mass of 1.9 +0.5 −0.4 × 10 10 M ⊙ , which agrees with CO-based estimates, providing an estimate of the CO-to-H 2 conversion factor of α CO = 0.8 ± 0.2 M ⊙ pc −2 (K km s −1) −1 ; an updated stellar mass of M * = 2.6 ± 0.5 × 10 10 M ⊙ ; and star formation rates averaged over 10 and 100 Myr of ⟨SFR⟩ 10 = 1340 ± 100 M ⊙ yr −1 and ⟨SFR⟩ 100 = 740 ± 80 M ⊙ yr −1 , respectively. The H 2 emission seems to be powered predominantly by shocks and star formation within the central ∼ 20 kpc, induced by stellar feedback and radio jets from the active galactic nucleus. Additionally, we find nearly an order of magnitude drop in the star formation rates estimated by PAH fluxes in cool core BCGs compared to field galaxies, suggesting that hot particles from the intracluster medium are destroying PAH grains even in the centralmost 10s of kpc.

Citation

Reefe, M., Mcdonald, M., Chatzikos, M., Seebeck, J., Mushotzky, R., Veilleux, S., Allen, S. W., Bayliss, M., Calzadilla, M., Canning, R., Donahue, M., Floyd, B., Gaspari, M., Hlavacek-Larrondo, J., Mcnamara, B., Russell, H., Sarkar, A., Sharon, K., & Somboonpanyakul, T. (in press). Cold Gas and Star Formation in the Phoenix Cluster with JWST. Astrophysical Journal,

• Journal Article Type: Article
• Acceptance Date: Jul 9, 2025
• Deposit Date: Jul 10, 2025
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Public URL: https://nottingham-repository.worktribe.com/output/51346513
• Publisher URL: https://iopscience.iop.org/journal/0004-637X