Related papers: Investigating Galaxy Clusters through Gamma-ray Em…
The total luminosity and spectral shape of the non-thermal emission produced by cosmic rays depends on their interstellar environment, a dependence that gives rise to correlations between galaxies' bulk properties -- star formation rate,…
A model for high-energy (>10^14 eV) cosmic rays (HECRs) from galactic and extragalactic gamma-ray bursts (GRBs) is summarized. Relativistic outflows in GRBs are assumed to inject power-law distributions of CR protons and ions to the highest…
Cosmic rays (CRs) are ubiquitous in the interstellar medium (ISM) of nearby galaxies, but many of their properties are not well-constrained. Gamma-ray observations provide a powerful tool in this respect, allowing us to constrain both the…
For more than a decade now the complete origin of the diffuse gamma-ray emission background (EGRB) has been unknown. Major components like unresolved star-forming galaxies (making <50% of the EGRB) and blazars (<23%), have failed to explain…
Massive black holes at the centers of galaxies can launch powerful wide-angle winds that, if sustained over time, can unbind the gas from the stellar bulges of galaxies. These winds may be responsible for the observed scaling relation…
Clusters of galaxies can potentially produce cosmic rays (CRs) up to very-high energies via large-scale shocks and turbulent acceleration. Due to their unique magnetic-field configuration, CRs with energy $\leq 10^{17}$ eV can be trapped…
We investigate the production of cosmic ray (CR) protons at cosmological shocks by performing, for the first time, numerical simulations of large scale structure formation that include directly the acceleration, transport and energy losses…
A diffuse non-thermal component has now been observed in massive merging clusters. To better characterise this component, and to extend analyses done for massive clusters down to a lower mass regime, we are conducting a statistical analysis…
Possible existence of extragalactic ultra-high energy cosmic ray sources giving a very small particle flux on the Earth is considered. Accretion discs around supermassive black holes where particles are accelerated in electric fields are…
The Energetic Gamma-Ray Experiment Telescope (EGRET) experiment onboard the Compton Gamma-Ray Observatory (CGRO) has provided the most precise measurements of the gamma-ray sky to date. The EGRET measurements of the diffuse emission across…
Galaxy clusters are the most massive constituents of the large-scale structure of the Universe. While the hot thermal gas that pervades galaxy clusters is relatively well understood through observations with X-ray satellites, our…
In the hierarchical structure formation model, clusters of galaxies form through a sequence of mergers and continuous mass accretion, which generate significant random gas motions especially in their outskirts where material is actively…
The outskirts of galaxy clusters are continuously disturbed by mergers and gas infall along filaments, which in turn induce turbulent flow motions and shock waves. We examine the properties of shocks that form within $r_{200}$ in sample…
Galaxy clusters (GCs) are the largest and most massive gravitationally bound objects in the large-scale structure of the Universe. Due to keV temperatures of virialized gas in the intracluster medium (ICM) and presence of cosmic rays (CRs),…
The interaction of magnetic turbulence and relativistic particles is a important process for understanding particles propagation and acceleration in many astrophysical environments. Large-scale turbulence can be generated in the…
While rich clusters are powerful sources of X-rays, gamma-ray emission from these large cosmic structures has not been detected yet. X-ray radiative energy losses in the central regions of relaxed galaxy clusters are so strong that one…
Observations of radio halos and relics in galaxy clusters indicate efficient electron acceleration. Protons should likewise be accelerated, suggesting that clusters may also be sources of very high-energy (VHE; E>100 GeV) gamma-ray…
Recent observations of the Galactic center in high-energy gamma-rays (above 0.1TeV) have opened up new ways to study this region, from understanding the emission source of these high-energy photons to constraining the environment in which…
Observations of the Galactic Center (GC) region in very-high-energy (VHE, >100 GeV) gamma rays, conducted with the High Energy Stereoscopic System (H.E.S.S.), led to the detection of an extended region of diffuse gamma-ray emission in 2006.…
In the next years the FERMI gamma ray telescope and the Cherenkov telescopes will put very stringent constraints to models of gamma ray emission from galaxy clusters providing crucial information on relativistic particles in the…