Self-Similar Shocks and Winds in Galaxy Clusters

TL;DR

This paper develops a theoretical model for large-scale shocks and flows in galaxy clusters, considering two coupled fluids—hot gas and dark matter—and explores their dynamics and observational implications.

Contribution

It introduces a self-similar two-fluid flow model with shocks in galaxy clusters, including dark matter shocks detectable via gravitational lensing, extending static models to dynamic, large-scale phenomena.

Findings

Existence of large-scale shocks in galaxy clusters inferred from X-ray and radio observations.

Dark matter shocks could produce observable gravitational lensing effects.

Various flow behaviors (outflows, inflows, static) depend on model parameters and shock locations.

Abstract

A theoretical model framework of spherical symmetry is presented for a composite astrophysical system of two polytropic fluids coupled together by gravity to explore large-scale shocks and flow dynamics in clusters of galaxies or in globular clusters. The existence of such large-scale shocks in clusters of galaxies as inferred by high-resolution X-ray and radio imaging observations implies large-scale systematic flows that are beyond usual static models for clusters of galaxies. Here, we explore self-similar two-fluid flow solutions with shocks for a hot polytropic gas flow in a cluster of galaxies in the presence of a massive dark matter (DM) flow after the initiation of a gravitational core collapse or a central AGN activity or a large-scale merging process. In particular, the possibility of DM shocks or sharp jumps of mass density and of velocity dispersion in dark matter halo is discussed and such DM shocks might be detectable through gravitational lensing effects. To examine various plausible scenarios for clusters of galaxies, we describe three possible classes of shock flows within our model framework for different types of temperature, density and flow speed profiles. Depending upon sensible model parameters and shock locations, the hot ICM and DM halo may have various combinations of asymptotic behaviours of outflow, breeze, inflow, contraction or static envelopes at large radii at a given time. We refer to asymptotic outflows of hot ICM at large radii as the galaxy cluster wind. As a result of such galaxy cluster winds and simultaneous contractions of DM halo during the course of galaxy cluster evolution, there would be less hot ICM within clusters of galaxies as compared to the average baryon fraction in the Universe.