James Webb Space Telescope Feed Post

Arxiv: Cold Gas and Star Formation in the Phoenix Cluster with JWST Published: 1/15/2025 4:36:34 AM Updated: 1/15/2025 4:36:34 AM

Paper abstract: We present integral field unit observations of the Phoenix Cluster with theJWST Mid-infrared Instrument's Medium Resolution Spectrometer (MIRI/MRS). Wefocus this study on the molecular gas, dust, and star formation in thebrightest cluster galaxy (BCG). We use precise spectral modeling to producemaps of the silicate dust, molecular gas, and polycyclic aromatic hydrocarbons(PAHs) in the inner ~50 kpc of the cluster. We have developed a novelmethod for measuring the optical depth from silicates by comparing the observedH_2 line ratios to those predicted by excitation models. We provide updatedmeasurements of the total molecular gas mass of 2.2^{+0.4}_{-0.1} \times10^{10} {\rm M}_\odot, which agrees with CO-based estimates, providing anestimate of the CO-to-H_2 conversion factor of \alpha_{\rm CO} = 0.9 \pm0.2\,{\rm M}_{\odot}\,{\rm pc}^{-2}\,({\rm K}\,{\rm km}\,{\rm s}^{-1})^{-1};an updated stellar mass of M_* = 2.6 \pm 0.5 \times 10^{10} {\rm M}_\odot;and star formation rates averaged over 10 and 100 Myr of \langle{\rmSFR}\rangle_{\rm 10} = 1340 \pm 100 {\rm M}_\odot\,{\rm yr}^{-1} and\langle{\rm SFR}\rangle_{\rm 100} = 740 \pm 80 {\rm M}_\odot\,{\rmyr}^{-1}, respectively. The H_2 emission seems to be powered predominantlyby star formation within the central ~ 20 kpc, with no need for an extraparticle heating component as is seen in other BCGs. Additionally, we findnearly an order of magnitude drop in the star formation rates estimated by PAHfluxes in cool core BCGs compared to field galaxies, suggesting that hotparticles from the intracluster medium are destroying PAH grains even in thecentralmost 10s of kpc.