Turbulence in Simulated Local Cluster Analogs: One-to-one comparisons between SLOW and XRISM/Hitomi

Abstract

The XRISM Resolve X-ray spectrometer allows to gain detailed insight into gas motions of the intra cluster medium (ICM) of galaxy clusters. Current simulation studies focus mainly on statistical comparisons, making the comparison to the currently still small number of clusters difficult due to unknown selection effects. This study aims to bridge this gap, using simulated counterparts of Coma, Virgo, and Perseus from the SLOW constrained simulations. These clusters show excellent agreement in their properties and dynamical state with observations, thus providing an ideal testbed to understand the processes shaping the properties of the ICM. We find that the simulations match the order of the amount of turbulence for the three considered clusters, Coma being the most active, followed by Perseus, while Virgo is very relaxed. Typical turbulent velocities are a few $\approx100$ km s$^{-1}$, very close to observed values. The resulting turbulent pressure support is $\approx1\%$ for Virgo, $\approx 6\%$ for Perseus, and $\approx 8\%$ for Coma within the central $1-2\%$ of $R_{200}$. Compared to previous simulations and observations, measured velocities and turbulent pressure support are on average lower, in line with XRISM findings, thus indicating the importance of selection effects.

Figures (5)

• Figure 1: Relaxation criteria according to Cui+2017Cui+2018 (top), and YuanHan2020 (bottom) for simulated Coma, Virgo, and Perseus analogs. The points indicate the redshifts of snapshots, for which data are derived. The connecting lines are meant to guide the eye, but do not contain physical information. The opacity of the lines/points indicates the evolution from $z=1.0$ (low opacity) to $z=0$ (high opacity). The dashed lines denote the thresholds for each criterion. Relaxed clusters lie within the gray area. Observed values by Yuan+2022 are shown as stars for comparison.
• Figure 2: Radial total and multi-scale filtered, turbulent velocity profiles at redshift $z=0$ (solid lines). Same colors as in Fig. \ref{['fig:dynamical_state']}. Observed velocity dispersions (right) and combined dispersions and bulk-motions (left) by XRISM/Hitomi (cyan) and XRISM (red) are overplotted as a comparison (straight lines with variance).
• Figure 3: Radial turbulent pressure profile of all clusters at redshift $z=0$. Same colors as in Fig. \ref{['fig:dynamical_state']}. Active clusters are shown with a dashed line, while relaxed clusters are indicated by a solid line. Observed turbulent pressure fractions by Hitomi (cyan) and XRISM (red) are overplotted as a comparison. In addition, mean values for relaxed (solid black) and active (daßshed black) clusters by Groth+2025a obtained with the multi-scale filtering are shown, including the central $1\sigma$ scatter as an errorbar.
• Figure 4: Broadband mock X-ray spectrum (top) and iron He$\alpha$ and Ly$\alpha$ line complexes (bottom) simulated with Phox. Same colors as in Fig. \ref{['fig:dynamical_state']}. The position of the spectral lines shifted only due to the mean redshift of the cluster galaxies is shown as vertical lines. At low opacity as a solid line, we overplot the spectra at larger filtering length corresponding to $z=0.08$, scaled down to similar total emission. The black solid line shows the XSPEC fit of the spectrum.
• Figure 5: Mock X-ray images created with SMAC with tabulated cooling tables SutherlandDopita1993 in the energy band from $0.5$ to $7$ keV. The dashed circle denotes $R_{\rm vir}$, and the arrow the north direction in J2000 coordinates. The black squares indicate the location of the XRISM pointings.