Gas rotation in galaxy clusters: signatures and detectability in X-rays

TL;DR

This study models differential gas rotation in galaxy clusters and assesses the potential for X-ray observations, especially with ASTRO-H, to detect and measure such rotation velocities.

Contribution

It introduces models of rotating intracluster medium and evaluates their detectability with current and future X-ray instruments.

Findings

Rotation velocities up to ~600 km/s are consistent with observed cluster ellipticities.

ASTRO-H can detect ICM rotation velocities as low as ~100 km/s.

X-ray isophote flattening can indicate gas rotation in galaxy clusters.

Abstract

We study simple models of massive galaxy clusters in which the intracluster medium (ICM) rotates differentially in equilibrium in the cluster gravitational potential. We obtain the X-ray surface brightness maps, evaluating the isophote flattening due to the gas rotation. Using a set of different rotation laws, we put constraint on the amplitude of the rotation velocity, finding that rotation curves with peak velocity up to \sim 600 km s^-1 are consistent with the ellipticity profiles of observed clusters. We convolve each of our models with the instrument response of the X-ray Calorimeter Spectrometer on board the ASTRO-H to calculate the simulated X-ray spectra at different distance from the X-ray centre. We demonstrate that such an instrument will allow us to measure rotation of the ICM in massive clusters, even with rotation velocities as low as \sim 100 km s^-1