Constraints on Cosmic Ray Transport in Galaxy Clusters from Radio and Gamma Ray Observations

Abstract

The nature of cosmic rays (CRs) and cosmic ray transport in galaxy clusters is probed by a number of observations. Radio observations reveal the synchrotron radiation of cosmic ray electrons (CRe) spiraling around cluster magnetic fields. $\gamma$-ray observations reveal hadronic reactions of cosmic ray protons (CRp) with ambient gas nuclei which produce pions. To date, no such cluster-wide $\gamma$-ray signal has been measured, putting an upper limit on the density of CRp present in clusters. But the presence of CRe implies some source of CRp, and consequently there must be some CRp loss mechanism. In this paper we quantify the observational constraints on this loss mechanism assuming that losses are dominated by CR transport, ultimately deriving a minimum diffusion coefficient of $\sim 10^{31}$ cm${}^2$ s${}^{-1}$ in the Coma cluster. This lower limit on transport may help illuminate some unknown properties of the cluster field topology. Conversely, measurements of cluster field tangling scales can constrain other model parameters, such as the relative acceleration efficiency of protons to electrons. To be consistent with the Coma observations, protons cannot be accelerated more than 15 times more efficiently than electrons of the same energy.

References in corpus (17)

• Energy spectra of gamma-rays, electrons and neutrinos produced at proton-proton interactions in the very high energy regime
• Cosmic rays in galaxy clusters and their non-thermal emission
• The Coma cluster magnetic field from Faraday rotation measures
• Feedback Heating by Cosmic Rays in Clusters of Galaxies
• Clusters of Galaxies as a Storage Room for Cosmic Rays
• A Bayesian view on Faraday rotation maps - Seeing the magnetic power spectra in galaxy clusters
• The diffuse radio emission from the Coma cluster at 2.675 GHz and 4.85 GHz
• Cosmic ray transport in galaxy clusters: implications for radio halos, gamma-ray signatures, and cool core heating
• Diffuse Radio Emission in/around the Coma Cluster: Beyond Simple Accretion
• Simulating cosmic rays in clusters of galaxies - II. A unified scheme for radio halos and relics with predictions of the gamma-ray emission
• Cosmic Ray Streaming in Clusters of Galaxies
• Search for gamma-ray emission from the Coma Cluster with six years of Fermi-LAT data
• Probing the origin of giant radio halos through radio and gamma-ray data : the case of the Coma cluster
• Probing the cosmic-ray content of galaxy clusters by stacking Fermi-LAT count maps
• Interaction of Cosmic Rays with Cold Clouds in Galactic Halos
• High $\beta$ Effects on Cosmic Ray Streaming in Galaxy Clusters
• The Transport of Cosmic Rays Across Magnetic Fieldlines

Cited by in corpus (7)

• Which AGN Jets Quench Star Formation in Massive Galaxies?
• Cosmic Rays or Turbulence can Suppress Cooling Flows (Where Thermal Heating or Momentum Injection Fail)
• Magnetohydrodynamic-Particle-in-Cell Simulations of the Cosmic-Ray Streaming Instability: Linear Growth and Quasi-linear Evolution
• The Impact of Cosmic Rays on the Kinematics of the Circumgalactic Medium
• The Role of Pressure Anisotropy in Cosmic Ray Hydrodynamics
• Searching for High-Energy Neutrino Emission from Galaxy Clusters with IceCube
• Magnetic fields in the intracluster medium with TNG-Cluster: properties, morphology, and tangential anisotropy