Relativistic protons in the Coma galaxy cluster: first gamma-ray constraints ever on turbulent reacceleration

Abstract

The Fermi-LAT collaboration recently published deep upper limits to the gamma-ray emission of the Coma cluster, a cluster that hosts the prototype of giant radio halos. In this paper we extend previous studies and use a formalism that combines particle reacceleration by turbulence and the generation of secondary particles in the intracluster medium to constrain relativistic protons and their role for the origin of the radio halo. We conclude that a pure hadronic origin of the radio halo is clearly disfavoured as it would require magnetic fields that are too strong. For instance $B_0>21\mu$G is found in the cluster center assuming that the magnetic energy density scales with thermal density, to be compared with $B_0\sim 4-5\mu$G as inferred from Rotation Measures (RM) under the same assumption. However secondary particles can still generate the observed radio emission if they are reaccelerated. For the first time the deep gamma-ray limits allow us to derive meaningful constraints if the halo is generated during phases of reacceleration of relativistic protons and their secondaries by cluster-scale turbulence. In this paper we explore a relevant range of parameter-space of reacceleration models. Within this parameter space a fraction of model configurations is already ruled out by current gamma-ray limits, including the cases that assume weak magnetic fields in the cluster core, $B\le 2-3\mu$G. Interestingly, we also find that the flux predicted by a large fraction of model configurations that assume a magnetic field consistent with RM is not far from the limits. This suggests that a detection of gamma rays from the cluster might be possible in the near future, provided that the electrons generating the radio halo are secondaries reaccelerated and the magnetic field in the cluster is consistent with that inferred from RM.

22 pages, 12 figures, submitted

References in corpus (16)

• The Quiescent Intracluster Medium in the Core of the Perseus Cluster
• A Catalog of Galaxy Clusters Observed by XMM-Newton
• Compressible Turbulence in Galaxy Clusters: Physics and Stochastic Particle Re-acceleration
• Parameterization of Gamma, e^+/- and Neutrino Spectra Produced by p-p Interaction in Astronomical Environment
• Shock Waves in Eulerian Cosmological Simulations: Main Properties and Acceleration of Cosmic Rays
• Simulating cosmic rays in clusters of galaxies - II. A unified scheme for radio halos and relics with predictions of the gamma-ray emission
• Cosmological Shocks in Adaptive Mesh Refinement Simulations and the Acceleration of Cosmic Rays
• Turbulence and Vorticity in Galaxy Clusters Generated by Structure Formation
• Turbulence and Particle Acceleration in Giant Radio Haloes: the Origin of Seed Electrons
• Gamma rays from clusters of galaxies
• The Matryoshka Run (II): Time Dependent Turbulence Statistics, Stochastic Particle Acceleration and Microphysics Impact in a Massive Galaxy Cluster
• Self-similar energetics in large clusters of galaxies
• High-energy gamma-ray and neutrino backgrounds from clusters of galaxies and radio constraints
• Cross-correlating the gamma-ray sky with catalogs of galaxy clusters
• Can giant radio halos probe the merging rate of galaxy clusters?
• Features of collisionless turbulence in the intracluster medium from simulated Faraday rotation maps II: the effects of instabilities feedback

Cited by in corpus (24)

• Diffuse Radio Emission from Galaxy Clusters
• Deep VLA observations of the cluster 1RXS J0603.3+4214 in the frequency range 1-2 GHz
• The Planck clusters in the LOFAR sky. I. LoTSS-DR2: new detections and sample overview
• Second order Fermi reacceleration mechanisms and large scale synchrotron radio emission in intra-cluster bridges
• Fast magnetic field amplification in distant galaxyclusters
• Shocks and non-thermal particles in clusters of galaxies
• Physical insights from the spectrum of the radio halo in MACS J0717.5+3745
• The ultra-steep diffuse radio emission observed in the cool-core cluster RX J1720.1+2638 with LOFAR at 54 MHz
• Revived Fossil Plasma Sources in Galaxy Clusters
• Radio and X-ray connection in radio mini-halos: implications for hadronic models
• New giant radio sources and underluminous radio halos in two galaxy clusters
• Recent Progress in Modeling the Macro- and Micro-Physics of Radio Jet Feedback in Galaxy Clusters
• High $\beta$ Effects on Cosmic Ray Streaming in Galaxy Clusters
• A three-component giant radio halo: the puzzling case of the galaxy cluster Abell 2142
• Limiting the shock acceleration of cosmic-ray protons in the ICM
• Diffuse Radio Emission from Galaxy Clusters in the LOFAR Two-metre Sky Survey Deep Fields
• A Massive Cluster at z = 0.288 Caught in the Process of Formation: The Case of Abell 959
• Extragalactic Observatory Science with the ASTRI Mini-Array at the Observatorio del Teide
• LOFAR Detection of a Low-Power Radio Halo in the Galaxy Cluster Abell 990
• On the Challenges of Cosmic-Ray Proton Shock Acceleration in the Intracluster Medium
• Double radio relics and radio halo in the high redshift galaxy cluster El Gordo with the Upgraded GMRT
• A low-frequency radio halo survey of the South Pole Telescope SZ-selected clusters with the GMRT
• Gamma-ray detection toward the Coma cluster with Fermi-LAT: Implications for the cosmic ray content in the hadronic scenario
• A LOFAR-uGMRT spectral index study of distant radio halos