Related papers: GeV $\gamma$-ray emission from M33 and Arp~299
The interaction between a supernova ejecta and the circum-stellar medium drives a strong shock wave which accelerates particles (i.e., electrons and protons). The radio and X-ray emission observed after the supernova explosion constitutes…
Recent observations have shown that pulsars are surrounded by extended regions which emit TeV-scale gamma rays through the inverse Compton scattering of very high energy electrons and positrons. Such TeV halos are responsible for a large…
Numerous extended sources around Galactic pulsars have shown significant $\gamma$-ray emission from GeV to TeV energies, revealing hundreds of TeV energy electrons scattering off of the underlying photon fields through inverse Compton…
Diffuse $\gamma$-ray emission is the most prominent observable signature of celestial cosmic-ray interactions at high energies. While already being investigated at GeV energies over several decades, assessments of diffuse $\gamma$-ray…
The Fermi gamma-ray satellite has recently detected gamma-ray emissions from radio galaxy cores. From these samples, we first examine the correlation between the luminosities at 5 GHz, L_{5GHz}, and at 0.1-10 GeV, L_{gamma}, of these…
We argue that gamma-ray bursts (GRBs) may be the origin of the cosmic gamma-ray background radiation observed in GeV range. It has theoretically been discussed that protons may carry a much larger amount of energy than electrons in GRBs,…
Star-forming galaxies, due to their high star-formation rates and hence large number of supernova remnants therein, are huge reservoirs of cosmic rays (CRs). These CRs collide with gases in the galaxies and produce high-energy neutrinos…
Starburst galaxies have a highly increased star-formation rate compared to regular galaxies and inject huge amounts of kinetic power into the interstellar medium via supersonic stellar winds, and supernova explosions. Supernova remnants,…
Context. Near a dozen star-forming galaxies have been detected in gamma-rays by the Fermi observatory in the last decade. A remarkable property of this sample is the quasi-linear relation between the gamma-ray luminosity and the star…
The observational progress in the $\gamma$-ray astronomy in the last few years has led to the discovery of more than a thousand sources at GeV energies and more than a hundred sources at TeV energies. A few different classes of compact…
We present two models for the cosmological UV background light, and calculate the opacity of GeV gamma--rays out to redshift 9. The contributors to the background include 2 possible quasar emissivities, and output from star--forming…
TeV gamma-rays were recently detected from the nearby normal spiral galaxy NGC 253 (Itoh et al., 2002). Observations to detect the Cherenkov light images initiated by gamma-rays from the direction of NGC 253 were carried out in 2000 and…
The nearby Large Magellanic Cloud (LMC) provides a rare opportunity of a spatially resolved view of an external star-forming galaxy in gamma-rays. The LMC was detected at 0.1-100GeV as an extended source with CGRO/EGRET and using early…
Cosmic rays of energies up to a few PeV are believed to be of galactic origin, yet individual sources have still not been firmly identified. Due to inelastic collisions with the interstellar gas, cosmic-ray nuclei produce a diffuse flux of…
Over the past decade, our knowledge of the \gamma-ray sky has been revolutionized by ground- and space-based observatories by detecting photons up to several hundreds of tera-electron volt (TeV) energies. A major population of the…
The origin of the inner Galactic emission, measured by COMPTEL with a flux of $\sim ~ 10^{-2}$ MeV cm$^{-2}$ s$^{-1}$ sr$^{-1}$ in the 1-30 MeV range, has remained unsettled since its discovery in 1994. We investigate the origin of this…
We report the detection of GeV gamma-ray emission from the molecular cloud complex that surrounds the supernova remnant (SNR) W44 using the Large Area Telescope (LAT) onboard Fermi. While the previously reported gamma-ray emission from SNR…
We report the detection of high-energy $\gamma$-ray emission in the vicinity of G172.8+1.5, which is debated as a Supernova remnant (SNR) or an ionized hydrogen (H$_{\rm{II}}$) region. Using 16-yr Pass 8 data from Fermi Large Area Telescope…
The solar disk is a bright source of multi-GeV gamma rays, due to the interactions of hadronic cosmic rays with the solar atmosphere. However, the underlying production mechanism is not understood, except that its efficiency must be greatly…
Galaxy clusters can be sources of high-energy (HE) $\gamma$-ray radiation, due to the efficient acceleration of particles exceeding EeV energies. At present, though, the only candidate for emitting HE $\gamma$-rays is the Coma cluster,…