Structure and turbulence in simulated galaxy clusters and the implications for the formation of radio haloes

Abstract

We track the histories of massive clusters of galaxies formed within a cosmological hydrodynamic simulation. Specifically, we track the time evolution of the energy in random bulk motions of the intracluster medium and X‐ray measures of cluster structure and their relationship to cluster mergers. We aim to assess the viability of the turbulent re‐acceleration model for the generation of giant radio haloes by comparing the level of turbulent kinetic energy in simulated clusters with the observed properties of radio halo clusters, giving particular attention to the association of radio haloes to clusters with disturbed X‐ray structures. The evolution of X‐ray cluster structure and turbulence kinetic energy, k, in simulations can then inform us about the expected lifetime of radio haloes and the fraction of clusters as a function of redshift expected to host them. We find strong statistical correlation of disturbed structure measures and the presence of enhancements in k. Specifically, quantitatively ‘disturbed’, radio halo‐like X‐ray morphology in our sample indicates a 92 per cent chance of the cluster in question having k elevated to more than twice its minimum value over the cluster’s life. The typical lifetime of episodes of elevated turbulence is on the order of 1 Gyr, though these periods can last 5 Gyr or more. This variation reflects the wide range of cluster histories; while some clusters undergo complex and repeated mergers spending a majority of their time in elevated k states, other clusters are relaxed over nearly their entire history. We do not find a bimodal relationship between cluster X‐ray luminosity and the total energy in turbulence that might account directly for a bimodal LX–P1.4 GHz relation. However, our result may be consistent with the observed bimodality, as here we are not including a full treatment of cosmic ray sources and magnetic fields.

Role of intracluster supernovae in radio mini-haloes in galaxy clusters

“…In high density (∼ 10 −2 cm −3 ) core such as in the Perseus cluster, the loss time-scales of the fossil electron population required in the re-acceleration models could be short (≤ 1 Gyr;Sarazin 1999;Pinzke, Peng Oh & Pfrommer 2017). As turbulent re-acceleration is sustainable on time-scales of < 1 Gyr (Hallman & Jeltema 2011) from the time of injection of the turbulence, fresh injections of suprathermal/mildlyrelativistic particles as well as turbulence are required to sustain the radio emission over periods ≥ 1 Gyr. The spatially and temporally distributed IC-SNIa remnants in the ICM can continuously inject a fresh population of electrons and turbulence required in the re-acceleration models.…”

Probing the Curious Case of a Galaxy Cluster Merger in Abell 115 with High-fidelity Chandra X-Ray Temperature and Radio Maps

“…In Hallman & Jeltema (2011), we extracted 16 simulated clusters at z = 0 whose mass exceeded M 200 ≥ 3 × 10 14 M . The objects of highest virial mass in the simulation are similar in mass to A115.…”

Multiscale analysis of turbulence evolution in the density-stratified intracluster medium

“…Turbulent motions in the intracluster medium (ICM) are an essential piece of puzzle in many astrophysical questions such as the non-thermal pressure and cluster cosmology (Lau et al 2009;Battaglia et al 2012;Nelson et al 2014a,b;Shi & Komatsu 2014), kinetic AGN feedback (Banerjee & Sharma 2014;Yang & Reynolds 2016;Zhang et al 2018), solution to the cooling flow problem (Dennis & Chandran 2005;Zhuravleva et al 2014aZhuravleva et al , 2017, galaxy -intracluster medium interaction (El-Zant et al 2004;Kim 2007), diffusion of chemical elements and heat (Ruszkowski & Oh 2010), generation of intergalactic magnetic fields (Carilli & Taylor 2002;Enßlin & Vogt 2006;Subramanian et al 2006;Iapichino & Niemeyer 2008;Cho 2014;Beresnyak & Miniati 2016;Vazza et al 2018), and acceleration of cosmic rays and the cluster radio emissions (Fujita et al 2003;Kang et al 2007;Hallman & Jeltema 2011;Brunetti & Lazarian 2011;Vazza et al 2011).…”