Shock Acceleration Model with Postshock Turbulence for Giant Radio Relics

Abstract

We explore the shock acceleration model for giant radio relics, in which relativistic electrons are accelerated via diffusive shock acceleration (DSA) by merger-driven shocks in the outskirts of galaxy clusters. In addition to DSA, turbulent acceleration by compressive MHD mode downstream of the shock is included as well as energy losses of postshock electrons by Coulomb scattering, synchrotron emission, and inverse Compton scattering off the cosmic background radiation. Considering that only a small fraction of merging clusters host radio relics, we favor the reacceleration scenario in which radio relics are generated preferentially when shocks encounter the regions containing low-energy (${\gamma }_{\mathrm{e}}\lesssim 300$) cosmic ray electrons (CRe). We perform time-dependent DSA simulations of spherically expanding shocks with physical parameters relevant for the Sausage radio relic, and calculate the radio synchrotron emission from the accelerated CRe. We find that significant level of postshock turbulent acceleration is required in order to reproduce broad profiles of the observed radio flux densities of the Sausage relic. Moreover, the spectral curvature in the observed integrated radio spectrum can be explained, if the putative shock should have swept up and exited out of the preshock region of fossil CRe about 10~Myr ago.

arXiv comment11 pages, 5 figures

References in corpus (17)

• Particle Acceleration on Megaparsec Scales in a Merging Galaxy Cluster
• Compressible Turbulence in Galaxy Clusters: Physics and Stochastic Particle Re-acceleration
• Diffusive Shock Acceleration Simulations of Radio Relics
• LOFAR, VLA, and Chandra observations of the Toothbrush galaxy cluster
• Giant radio relics in galaxy clusters: reacceleration of fossil relativistic electrons?
• Using double radio relics to constrain galaxy cluster mergers: A model of double radio relics in CIZA J2242.8+5301
• Challenges to our understanding of radio relics: X-ray observations of the Toothbrush cluster
• Particle reacceleration by compressible turbulence in galaxy clusters: effects of reduced mean free path
• Radio and X-ray Shocks in Clusters of galaxies
• Re-acceleration Model for Radio Relics with Spectral Curvature
• $Suzaku$ X-ray study of the double radio relic galaxy cluster CIZA J2242.8+5301
• The widest-frequency radio relic spectra: observations from 150 MHz to 30 GHz
• Abell 1033: birth of a radio phoenix
• The highest-frequency detection of a radio relic: 16-GHz AMI observations of the `Sausage' cluster
• Magnetic Field Evolution in Giant Radio Relics using the example of CIZA J2242.8+5301
• Shock Acceleration Model for the Toothbrush Radio Relic
• The impact of the SZ effect on cm-wavelength (1-30 GHz) observation of galaxy cluster radio relics

Cited by in corpus (7)

• Diffuse Radio Emission from Galaxy Clusters
• The MeerKAT Galaxy Cluster Legacy Survey I. Survey Overview and Highlights
• Twin radio relics in a near-by low-mass galaxy cluster Abell 168
• Effects of Alfvenic Drift on Diffusive Shock Acceleration at Weak Cluster Shocks
• On the Challenges of Cosmic-Ray Proton Shock Acceleration in the Intracluster Medium
• Reaching thermal noise at ultra-low radio frequencies: the Toothbrush radio relic downstream of the shock front
• Non-thermal emission in galaxy groups at extremely low frequency: the case of A1213