相关论文: Testing cosmic-ray acceleration with radio relics:…
Observations of galaxy clusters show radio emission extended over almost the system scale, necessitating mechanisms for particle acceleration. Previous models for acceleration such as diffusive shock acceleration and that due to turbulence…
Context: Cosmic ray acceleration in galaxy clusters is still an ongoing puzzle, with relativistic electrons forming radio relics at merger shocks and emitting synchrotron radiation. In the present work we perform hybrid-kinetic simulations…
Galaxy cluster merger shocks are the main agent for the thermalization of the intracluster medium and the energization of cosmic ray particles in it. Shock propagation changes the state of the tenuous intracluster plasma, and the…
We describe multiwavelength optical, X-ray and radio evidences of energetic mergers in southern galaxy cluster Abell 3376 (A3376, redshift z=0.046, X-ray luminosity $ \rm L_{X}(0.1-2.4 keV)= 2.48 \times 10^{44} erg s^{-1}$). Here we report…
Clusters of galaxies are sites of acceleration of charged particles and sources of non-thermal radiation. We report on new constraints on the population of cosmic rays in the Intra Cluster Medium (ICM) obtained via radio observations of a…
Radio galaxies play an important role in the seeding of cosmic rays and magnetic fields in galaxy clusters. Here, we simulate the evolution of relativistic electrons injected into the intracluster medium by radio galaxies. Using passive…
Radio relics are arc-like synchrotron sources at the periphery of galaxy clusters, produced by cosmic-ray electrons in a $\mu$G magnetic field which are believed to have been (re-)accelerated by merger shock fronts. However, not all relics…
Galaxy clusters are known to host many active galaxies (AGNs) with radio jets, which could expand to form radio bubbles with relativistic electrons in the intracluster medium (ICM). It has been suggested that fossil relativistic electrons…
The underlying physics of giant radio halos and mini halos in galaxy clusters is still an open question, which becomes more pressing with the growing number of detections. In this paper, we explore the possibility that radio-emitting…
We investigate numerically the contribution to the cosmic gamma-ray background from cosmic-rays ions and electrons accelerated at intergalactic shocks associated with cosmological structure formation. We show that the kinetic energy of…
In a previous paper (Brunetti et al. 2004) we presented the first self-consistent calculations of the time-dependent coupled equations for the electrons, hadrons and Alfv\'en waves in the intracluster medium, which describe the stochastic…
The properties of cosmic shock waves are studied through numerical simulations in two cosmological scenarios (SCDM and LCDM). The scaling relations for the average radius and velocity associated with the accretion shocks are somewhat…
Galaxy clusters host the largest particle accelerators in the Universe: Shock waves in the intracluster medium (ICM), a hot and ionised plasma, that accelerate particles to high energies. Radio observations pick up synchrotron emission in…
The nonthermal radiation observed from a handfull of clusters of Galaxies is the proof that particle acceleration occurs in the intracluster medium. It is often believed that shock surfaces associated with either mergers of clusters of…
About 1/3 of X-ray-luminous clusters show smooth, unpolarized radio emission on ~Mpc scales, known as giant radio halos. One promising model for radio halos is Fermi-II acceleration of seed relativistic electrons by turbulence of the…
The formation of collisionless shock fronts is an ubiquitous phenomenon in space plasma environments. In the solar wind shocks might accompany coronal mass ejections, while even more violent events, such as supernovae, produce shock fronts…
It is generally accepted that radio relics are the result of synchrotron emission from shock-accelerated electrons. Current models, however, are still unable to explain several aspects of their formation. In this paper, we focus on three…
We investigate the possibility that radio halos of clusters of galaxies are caused by synchrotron emission of cosmic ray electrons (CRe), which were produced by cosmic ray protons (CRp) interacting hadronically with the intra-cluster medium…
Radio mini-halos are diffuse, steep-spectrum synchrotron sources associated with relaxed clusters of galaxies. Observations of some mini-halo sources indicate a correlation between the radio emission and the X-ray signature of gas sloshing,…
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.…