Hard X-ray emission from accretion shocks around galaxy clusters

Abstract

We show that the hard X-ray (HXR) emission observed from several galaxy clusters is naturally explained by a simple model, in which the nonthermal emission is produced by inverse Compton scattering of cosmic microwave background photons by electrons accelerated in cluster accretion shocks: The dependence of HXR surface brightness on cluster temperature is consistent with that predicted by the model, and the observed HXR luminosity is consistent with the fraction of shock thermal energy deposited in relativistic electrons being \lesssim 0.1. Alternative models, where the HXR emission is predicted to be correlated with the cluster thermal emission, are disfavored by the data. The implications of our predictions to future HXR observations (e.g. by NuStar, Simbol-X) and to (space/ground based) gamma-ray observations (e.g. by Fermi, HESS, MAGIC, VERITAS) are discussed.

7 pages, 3 figures, somewhat revised, published in JCAP

References in corpus (14)

• Chandra temperature profiles for a sample of nearby relaxed galaxy clusters
• The impact of mergers on relaxed X-ray clusters - I. Dynamical evolution and emergent transient structures
• Cosmic ray feedback in hydrodynamical simulations of galaxy formation
• Simulating cosmic rays in clusters of galaxies - II. A unified scheme for radio halos and relics with predictions of the gamma-ray emission
• The impact of mergers on relaxed X-ray clusters - II. Effects on global X-ray and SZ properties and their scaling relations
• Simulated X-ray galaxy clusters at the virial radius: slopes of the gas density, temperature and surface brightness profiles
• Galaxy Clusters in the Swift/BAT era: Hard X-rays in the ICM
• Chemical evolution in Sersic 159-03 observed with XMM-Newton
• Nonthermal phenomena in clusters of galaxies
• Nonthermal Emission Associated with Strong AGN Outbursts at the Centers of Galaxy Clusters
• South-West extension of the hard X-ray emission from the Coma cluster
• X-ray observations of the Coma Cluster in a broad energy band with INTEGRAL, RXTE, and ROSAT observatories
• On the ICS interpretation of the Hard X-Ray Excesses in Galaxy Clusters: the case of Ophiuchus
• The Coma Cluster hard X-ray spectrum revisited: still no evidence for a hard tail

Cited by in corpus (13)

• NuSTAR Observations of the Bullet Cluster: Constraints on Inverse Compton Emission
• Using Radio Halos and Minihalos to Measure the Distributions of Magnetic Fields and Cosmic-Rays in Galaxy Clusters
• Quenching of Satellite Galaxies at the Outskirts of Galaxy Clusters
• Constraints on diffuse gamma-ray emission from structure formation processes in the Coma cluster
• Detection of virial shocks in stacked Fermi-LAT clusters
• The Lack of Diffuse, Nonthermal Hard X-ray Emission in the Coma Cluster: The Swift BAT's Eye View
• Preliminary evidence for a virial shock around the Coma galaxy cluster
• X-ray to gamma-ray virial shock signal from the Coma cluster
• Cosmic Ray Acceleration and Nonthermal Radiation at Accretion Shocks in the Outer Regions of Galaxy Clusters
• Coincident SZ and $\gamma$-ray signals from cluster virial shocks
• Optical inverse-Compton emission from clusters of galaxies
• The Blow-off Impulse Equivalence between Multi-Energy Composite Spectrum Electron Beam and Powerful Pulsed X-ray
• Particle Reacceleration by Turbulence and Radio Constraints on Multi-Messenger High-Energy Emission from the Coma Cluster