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Information on cosmic-ray (CR) composition comes from direct CR measurements while their distribution in the Galaxy is evaluated from observations of their associated diffuse emission in the range from radio to gamma rays. Even though the…

High Energy Astrophysical Phenomena · Physics 2019-03-06 Elena Orlando , Gudlaugur Johannesson , Igor V. Moskalenko , Troy A. Porter , Andrew Strong

Faint $\gamma$-ray signatures emerge in Fermi-LAT data stacked scaled to the characteristic $\theta_{500}$ angles of MCXC galaxy clusters. After Paper I of this series thus discovered virial shocks, later supported in other bands, this…

High Energy Astrophysical Phenomena · Physics 2025-11-06 Uri Keshet

We show that the well-known discrepancy between the radial dependence of the Galactic cosmic ray (CR) nucleon distribution, as inferred most recently from EGRET observations of diffuse gamma-rays above 100 MeV, and of the most likely CR…

Astrophysics · Physics 2009-11-07 D. Breitschwerdt , V. A. Dogiel , H. J. Voelk

Context: Diffuse $\gamma$-ray emission from cosmic ray (CR) protons scattering off the gas in the intracluster and intergalactic medium (ICM and IGM) remains out of reach for current observations. Detecting this emission would provide…

High Energy Astrophysical Phenomena · Physics 2025-10-20 Ludwig M. Böss , Ildar Khabibullin , Daniel Karner , Klaus Dolag , Ulrich P. Steinwandel , Elena Hernandez-Martinez , Jenny G. Sorce

An important contribution to the gamma-ray emission of our Galaxy is the Galactic Diffuse emission. We present specific developments within the PICARD code for modeling of Galactic cosmic ray propagation that are relevant for the…

High Energy Astrophysical Phenomena · Physics 2017-01-26 Felix Niederwanger , Olaf Reimer , Ralf Kissmann , Richard Tuffs

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…

Astrophysics · Physics 2007-06-05 B. M. Baughman , W. B. Atwood , R. P. Johnson , T. A. Porter , M. Ziegler

The all-sky survey in high-energy gamma rays (E$>$30 MeV) carried out by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma-Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray…

Astrophysics · Physics 2011-05-05 P. Sreekumar

We present a novel interpretation of the gamma-ray diffuse emission measured by H.E.S.S. in the Galactic Center (GC) region and the Galactic ridge. Our starting base is an updated analysis of PASS8 Fermi-LAT data, which allows to extend…

High Energy Astrophysical Phenomena · Physics 2017-07-27 D. Gaggero , D. Grasso , A. Marinelli , M. Taoso , A. Urbano , S. Ventura

Recent EGRET observations of the diffuse Galactic gamma-ray emission reveal a spectrum which is incompatible with the assumption that the cosmic ray spectra measured locally hold throughout the Galaxy: the spectrum above 1 GeV, where the…

Astrophysics · Physics 2009-11-07 I. Büsching , M. Pohl , R. Schlickeiser

High-energy gamma rays of interstellar origin are produced by the interaction of cosmic-ray (CR) particles with the diffuse gas and radiation fields in the Galaxy. The main features of this emission are well understood and are reproduced by…

High Energy Astrophysical Phenomena · Physics 2017-09-06 Troy A. Porter , Gudlaugur Johannesson , Igor V. Moskalenko

Multi-wavelength analyses of spectra of active galactic nuclei (AGNs) provide useful information on the physical processes in the accretion disk and jets of black holes. This, however, is limited to bright sources and may not represent the…

High Energy Astrophysical Phenomena · Physics 2021-06-09 Houdun Zeng , Vahé Petrosian , Tingfeng Yi

We present a two-parameter model of the extragalactic gamma-ray background (EGB) in the 0.1-100 GeV range as measured by the Large Area Telescope (LAT) onboard the Fermi satellite. The EGB can be fully explained as the sum of three distinct…

Cosmology and Nongalactic Astrophysics · Physics 2011-05-25 Massimo Cavadini , Ruben Salvaterra , Francesco Haardt

The all-sky survey in high-energy gamma rays (E > 30 MeV) carried out by the Energetic Gamma Ray Experiment Telescope (EGRET) aboard the Compton Gamma-Ray Observatory provides a unique opportunity to examine in detail the diffuse gamma-ray…

Astrophysics · Physics 2011-04-15 Yu. A. Golubkov , M. Yu. Khlopov

Gamma rays from extragalactic sources are attenuated by pair-production interactions with diffuse photons of the extragalactic background light (EBL). Gamma-ray bursts (GRBs) are a source of high-redshift photons above 10 GeV, and could be…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 Rudy C. Gilmore , Francisco Prada , Joel R. Primack

We report the Fermi-LAT discovery of high-energy (MeV/GeV) gamma-ray emission positionally consistent with the center of the radio galaxy M87, at a source significance of over 10 sigma in ten-months of all-sky survey data. Following the…

High Energy Astrophysical Phenomena · Physics 2009-12-04 The Fermi LAT Collaboration , A. A. Abdo , D. E. Harris , F. Massaro , L. Stawarz

The Large Area Telescope on the Fermi gamma-ray Space Telescope (FGST, ex-GLAST) provides unprecedented sensitivity for all-sky monitoring of gamma-ray activity. It is an adequate telescope to detect transient sources, since the observatory…

High Energy Astrophysical Phenomena · Physics 2010-08-25 Sylvain Chaty

We report a study of extended $\gamma$-ray emission with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope, which is likely to be the second case of a $\gamma$-ray detection from a star-forming region (SFR) in our…

High Energy Astrophysical Phenomena · Physics 2017-05-03 Junichiro Katsuta , Yasunobu Uchiyama , Stefan Funk

A recent re-analysis of EGRET data by Dixon et al. has led to the discovery of a statistically significant diffuse $\gamma$-ray emission from the galactic halo. We show that this emission can naturally be accounted for within a…

Astrophysics · Physics 2007-05-23 F. De Paolis , G. Ingrosso , Ph. Jetzer , M. Roncadelli

The first measurement on the antiproton to proton ratio made by the AMS-02 collaboration agrees with the expection from conventional cosmic-ray secondaries in the kinetic energy range $\sim 10-100$ GeV, which can be turned into stringent…

High Energy Physics - Phenomenology · Physics 2015-09-30 Hong-Bo Jin , Yue-Liang Wu , Yu-Feng Zhou

More than 90% of the Galactic gas-related gamma-ray emissivity above 1 GeV is attributed to the decay of neutral pions formed in collisions between cosmic rays and interstellar matter, with lepton-induced processes becoming increasingly…

High Energy Astrophysical Phenomena · Physics 2019-08-13 C. D. Dermer , A. W. Strong , E. Orlando , L. Tibaldo