Kavli Affiliate: Bradford A. Benson
| First 5 Authors: Charles Romero, Massimo Gaspari, Gerrit Schellenberger, Bradford A. Benson, Lindsey E. Bleem
| Summary:
The hot plasma in galaxy clusters, the intracluster medium (ICM), is expected
to be shaped by subsonic turbulent motions, which are key for heating, cooling,
and transport mechanisms. The turbulent motions contribute to the non-thermal
pressure which, if not accounted for, consequently imparts a hydrostatic mass
bias. Accessing information about turbulent motions is thus of major
astrophysical and cosmological interest. Characteristics of turbulent motions
can be indirectly accessed through surface brightness fluctuations. This study
expands on our pilot investigations of surface brightness fluctuations in the
SZ and X-ray by examining, for the first time, a large sample of 60 clusters
using both SPT-SZ and XMM-Newton data and span the redshift range $0.2 < z <
1.5$, thus constraining the respective pressure and density fluctuations within
0.6~$R_{500}$. We deem density fluctuations to be of sufficient quality for 32
clusters, finding mild correlations between the peak of the amplitude spectra
of density fluctuations and various dynamical parameters. We infer turbulent
velocities from density fluctuations with an average Mach number
$mathcal{M}_{text{3D}} = 0.52 pm 0.14$, in agreement with numerical
simulations. For clusters with inferred turbulent Mach numbers from both
pressure, $mathcal{M}_{text{P}}$ and density fluctuations,
$mathcal{M}_{rho}$, we find broad agreement between $mathcal{M}_{text{P}}$
and $mathcal{M}_{rho}$. Our results suggest a bimodal Mach number
distribution, with the majority of clusters being turbulence-dominated
(subsonic) while the remainder are shock-dominated (supersonic).
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