Kavli Affiliate: Erin Kara
| First 5 Authors: XRISM Collaboration, XRISM Collaboration, , ,
| Summary:
The dynamics of the intra-cluster medium (ICM), the hot plasma that fills
galaxy clusters, are shaped by gravity-driven cluster mergers and feedback from
supermassive black holes (SMBH) in the cluster cores. XRISM measurements of ICM
velocities in several clusters offer insights into these processes. We compare
XRISM measurements for nine galaxy clusters (Virgo, Perseus, Centaurus, Hydra
A, PKS,0745–19, A2029, Coma, A2319, Ophiuchus) with predictions from three
state-of-the-art cosmological simulation suites, TNG-Cluster, The Three Hundred
Project GADGET-X, and GIZMO-SIMBA, that employ different models of feedback. In
cool cores, XRISM reveals systematically lower velocity dispersions than the
simulations predict, with all ten measurements below the median simulated
values by a factor $1.5-1.7$ on average and all falling within the bottom
$10%$ of the predicted distributions. The observed kinetic-to-total pressure
ratio is also lower, with a median value of $2.2%$, compared to the predicted
$5.0-6.5%$ for the three simulations. Outside the cool cores and in
non-cool-core clusters, simulations show better agreement with XRISM
measurements, except for the outskirts of the relaxed, cool-core cluster A2029,
which exhibits an exceptionally low kinetic pressure support ($<1%$), with
none of the simulated systems in either of the three suites reaching such low
levels. The non-cool-core Coma and A2319 exhibit dispersions at the lower end
but within the simulated spread. Our comparison suggests that the three
numerical models may overestimate the kinetic effects of SMBH feedback in
cluster cores. Additional XRISM observations of non-cool-core clusters will
clarify if there is a systematic tension in the gravity-dominated regime as
well.
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