Kavli Affiliate: Michael McDonald
| First 5 Authors: Michael Reefe, Michael Reefe, , ,
| Summary:
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 $sim$50 kpc of the cluster. We measure the optical depth
from silicates by comparing the observed H$_2$ line ratios to those predicted
by excitation models. We provide updated measurements of the total molecular
gas mass of $1.9^+0.5_-0.4 times 10^10$ $M_odot$ which agrees with
CO-based estimates, providing an estimate of the CO-to-H$_2$ conversion factor
of $alpha_rm CO = 0.8 pm 0.2,M_odot,rm pc^-2,(rm K,rm
km,rm s^-1)^-1$; an updated stellar mass of $M_* = 2.6 pm 0.5 times
10^10$ $M_odot$; and star formation rates averaged over 10 and 100 Myr of
$langlerm SFRrangle_rm 10 = 1340 pm 100$ $M_odot,rm yr^-1$, and
$langlerm SFRrangle_rm 100 = 740 pm 80$ $M_odot,rm yr^-1$,
respectively. The H$_2$ emission seems to be powered predominantly by shocks
and star formation within the central $sim 20$ 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.
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