Related papers: Origin of Hydrogen Ionization in the 1 pc Galactic…
We study a possible connection between different non-thermal emissions from the inner few parsecs of the Galaxy. We analyze the origin of the gamma-ray source 2FGL J1745.6-2858 (or 3FGL J1745.6-2859c) in the Galactic Center and the diffuse…
Energetic gamma rays (GeV to TeV photon energy) have been detected toward several supernova remnants (SNR) associated with molecular clouds. If the gamma rays are produced mainly by hadronic processes rather than leptonic processes like…
A point-like source of ~TeV gamma-rays has recently been seen towards the Galactic center by HESS and other air Cerenkov telescopes. In recent work (Ballantyne et al. 2007), we demonstrated that these gamma-rays can be attributed to…
We report observations and analysis of infrared spectra of H3+ and CO lines in the Galactic center, within a few parsecs of the central black hole, Sgr A*. We find a cosmic ray ionization rate typically an order of magnitude higher than…
Pierre Auger experiment has observed a few cosmic ray events above 55 EeV from the direction of the core of Cen A. These cosmic rays might have originated from the core of Cen A. High energy gamma ray emission has been observed by HESS from…
The winds of ionized gas driven by Active Galactic Nuclei (AGN) can be studied through absorption lines in their X-ray spectra. A recurring feature of these outflows is their broad ionization distribution, including essentially all…
Diffuse galactic gamma-ray emission is produced by the interaction of cosmic rays (CRs) with the interstellar environment. The study of gamma-ray emission is therefore a powerful tool to investigate the origin of CRs and the processes…
We have developed in detail the theory of X-ray line and continuum production due to atomic interactions of accelerated ions, incorporating in our calculations information from a broad range of laboratory measurements. We applied our…
Context: Since a few years, signatures of supernova remnants associated with molecular clouds have been detected in gamma rays. Whether these gamma rays are generated by cosmic ray electrons or by cosmic ray protons is usually not known.…
High-energy (HE) and very high-energy (VHE) gamma-ray observations from the Galactic center (GC) detected extended emission correlated with the morphology of the central molecular zone (CMZ). Emission in both bands is expected to be…
We study the ionization process involving antiproton and hydrogen in the energy range between 0.1 keV to 500 keV, using single center close coupling approximation. We construct the scattering wave function using B-spline bases. The results…
The identification of Cosmic Ray (CR) sources represents one of the biggest and long-standing questions in astrophysics. Direct measurements of cosmic rays cannot provide directional information due to their deflection in (extra)galactic…
We discuss the origin of continuum and line X-ray emission observed in the direction the Galactic Center. We predict a significant flux of de-excitation gamma-ray lines in this direction, which can be produced by subrelativistic protons…
We discuss the production of $\gamma$-rays from cosmic rays (CR) in the circumgalactic medium (CGM) of Andromeda (M31) in light of the recent detection of $\gamma$-rays from an annular region of $\sim 5.5-120$ kpc away from the M31 disc. We…
The High Energy Stereoscopic System (HESS), the Major Atmospheric Gamma-ray Imaging Cherenkov Telescope (MAGIC), and the Very Energetic Radiation Imaging Telescope Array System (VERITAS) have observed diffuse gamma-ray emission strongly…
The rate of ionization by cosmic rays in interstellar gas directly associated with gamma-ray emitting supernova remnants is for the first time calculated to be several orders of magnitude larger than the Galactic average. Analysis of…
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.…
The origin of He II emission in galaxies remains a debated topic, requiring ionizing photons with energies exceeding 54 eV. While massive stars, such as Wolf-Rayet stars, have been considered potential sources, their UV flux often fails to…
Energetic gamma rays (GeV to TeV photon energy) have been detected toward several supernova remnants (SNR) that are associated with molecular clouds. If the gamma rays are produced mainly by hadronic processes rather than leptonic processes…
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…