Related papers: The quest for cosmic ray protons in galaxy cluster…
Galaxy clusters are considered to be gigantic reservoirs of cosmic rays (CRs). Some of the clusters are found with extended radio emission, which provides evidence for the existence of magnetic fields and CR electrons in the intra-cluster…
We propose a new hypothesis for the origin of the major part of non-solar hadronic cosmic rays (CRs) at all energies: highly relativistic, narrowly collimated jets from the birth or collapse of neutron stars (NSs) in our Galaxy accelerate…
The gas temperature in the cores of many clusters of galaxies drops inward by about a factor of three or more within the central 100 kpc radius. The radiative cooling time drops over the same region from 5 or more Gyr down to below a few…
High-precision measurements of the cosmic-ray (CR) proton and helium spectra have revealed significant deviations from a simple power law, characterized by multiple spectral features, including a hardening above $\sim$100~GeV, a broad…
The detection of diffuse radio emission associated with clusters of galaxies indicates populations of relativistic leptons infusing the intracluster medium. Those electrons and positrons are either injected into and accelerated directly in…
Clusters of galaxies host spectacular diffuse radio sources, extending over scales from 100 kpc to several Mpcs. These sources, with extremely faint surface brightness ($\mu$Jy/arcsec$^2$ level), are not tied to individual galaxies but…
The identification of major contributors to the locally observed fluxes of Cosmic Rays (CRs) is a prime objective towards the resolution of the long-standing enigma of CRs. We report on a compelling similarity of the energy and radial…
In about 70% of the population of relaxed, cool-core galaxy clusters, the brightest cluster galaxy (BCG) is radio loud, showing non-thermal radio jets and lobes ejected by the central active galactic nucleus (AGN). In recent years such…
Galaxy formation simulations demonstrate that cosmic-ray (CR) feedback may be important in the launching of galactic-scale winds. CR protons dominate the bulk of the CR population, yet most observational constraints of CR feedback come from…
We propose a new hypothesis for the origin of non-solar hadronic cosmic rays (CRs) at all energies: Highly relativistic, narrowly collimated jets from the birth or collapse of neutron stars (NSs) in our Galaxy accelerate ambient disk and…
We study the heating of the cool cores in galaxy clusters by cosmic-rays (CRs) accelerated by the central active galactic nuclei (AGNs). We especially focus on the stability of the heating. The CRs stream with Alfv\'en waves in the…
The vast majority of the celestial gamma-ray sources detected so far have not yet been identified with secure counterparts at other wavelenghts. Here we report the preliminary evidence of a probable association between galaxy clusters and…
This is the second of a series of three papers exploring the connection between the multiwavelength properties of AGN in nearby early-type galaxies and the characteristics of their hosts. In Capetti et al. (2005) we presented a study of the…
We are looking for radio `relics' and `halos' in an X-ray selected sample of clusters of galaxies. These radio features are not a product of the Active Galactic Nuclei (AGN)-mechanism, but more likely are associated with past cluster merger…
The GeV and TeV emission from M82 and NGC 253 observed by Fermi, HESS, and VERITAS constrains the physics of cosmic rays (CRs) in these dense starbursts. We argue that the gamma rays are predominantly hadronic in origin, as expected by…
Our Chandra X-ray Observatory archival study of intracluster entropy in a sample of 222 galaxy clusters shows that H-alpha and radio emission from the brightest cluster galaxy are much more pronounced when the cluster's core gas entropy is…
A recent detection of spatially extended gamma-ray emission in the central region of the Andromeda galaxy (M31) has led to several possible explanations being put forth, including dark matter annihilation and millisecond pulsars. Another…
Recent results from the HESS gamma ray telescope have shown the presence of both a diffuse, extended, flux of gamma rays above ~0.4 TeV and discrete sources in and near the Galactic Centre. Here, we put forward a possible explanation in…
In this letter we present a study of the central regions of cool-core clusters hosting radio mini-halos, which are diffuse synchrotron sources extended on cluster-scales surrounding the radio-loud brightest cluster galaxy. We aim to…
A joint hadronic model is shown to quantitatively explain the observations of diffuse radio emission from galaxy clusters in the form of minihalos, giant halos, relics, and their hybrid, transitional stages. Cosmic-ray diffusion of order…