学术文献库

While awaiting direct velocity measurement of gas motions in the hot intracluster medium, we rely on indirect probes, including gas perturbations in galaxy clusters. Using a sample of $\sim 80$ clusters in different dynamic states from Omega500 cosmological simulations, we examine scaling relations between the fluctuation amplitudes of gas density, $δρ/ρ$, pressure, $δP/P$, X-ray surface brightness, Sunyaev-Zeldovich (SZ) y-parameter, and the characteristic Mach number of gas motions, $M_{\rm 1d}$. In relaxed clusters, accounting for halo ellipticities reduces $δρ/ρ$ or $δP/P$ by a factor of up to 2 within $r_{500c}$. We confirm a strong linear correlation between $δρ/ρ$ (or $δP/P$) and $M_{\rm 1d}$ in relaxed clusters, with the proportionality coefficient $η\approx 1$. For unrelaxed clusters, the correlation is less strong and has a larger $η\approx 1.3\pm 0.5$ ($1.5\pm0.5$) for $δρ/ρ$ ($δP/P$). Examination of the power-law scaling of $M_{\rm 1d}$ with $δρ/ρ$ shows that it is almost linear for relaxed clusters, while for the unrelaxed ones, it is closer to $δρ/ρ\propto M_{\rm 1d}^2$, supporting an increasing role of non-linear terms and compressive modes. In agreement with previous studies, we observe a strong correlation of $M_{\rm 1d}$ with radius. Correcting for these correlations leaves a residual scatter in $M_{\rm 1d}$ of $\sim 4 (7)$ per cent for relaxed (perturbed) clusters. Hydrostatic mass bias correlates with $M_{\rm 1d}$ as strongly as with $δρ/ρ$ in relaxed clusters. The residual scatters after correcting for derived trends is $\sim 6-7$ per cent. These predictions can be verified with existing X-ray and SZ observations of galaxy clusters combined with forthcoming velocity measurements with X-ray microcalorimeters.