Resonant scattering in galaxy clusters for anisotropic gas motions on various spatial scales

TL;DR

This paper investigates how anisotropic hot gas motions in galaxy clusters influence resonant scattering of spectral lines, affecting line shapes and brightness profiles, with implications for measuring gas dynamics.

Contribution

It presents Monte Carlo radiative transfer calculations showing how different gas motion directions and scales impact resonant scattering in galaxy clusters.

Findings

Radial motions significantly reduce scattering efficiency.

Large-scale motions have minimal impact on scattering.

Uncertainty estimates for gas motion measurements are provided.

Abstract

The determination of characteristic amplitudes and anisotropy of hot gas motions in galaxy clusters from observations of the brightest resonance lines is discussed. Gas motions affect (i) the spectral line shape through the Doppler effect and (ii) the radial surface brightness profiles in lines during resonant scattering. Radiative transfer calculations have been performed by the Monte Carlo method in the FeXXV resonance line at 6.7 eV for the Perseus cluster (Abell426). It was shown that (a) radial motions reduce the scattering efficiency much more dramatically than purely tangential motions; (b) large-scale gas motions weakly affect the scattering efficiency. The uncertainty in measuring the characteristics of gas motions using resonant scattering has been estimated for existing and future observations of clusters.