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The presence of relativistic electrons within the diffuse gas phase of galaxy clusters is now well established, but their detailed origin remains unclear. Cosmic ray protons are also expected to accumulate during the formation of clusters…

High Energy Astrophysical Phenomena · Physics 2021-04-14 R. Adam , H. Goksu , S. Brown , L. Rudnick , C. Ferrari

Over the past 16 years, the Fermi Large Area Telescope (LAT) has significantly advanced our view of the GeV gamma-ray sky, yet several key questions remain - such as the composition of the isotropic gamma-ray background, the origin of the…

High Energy Astrophysical Phenomena · Physics 2025-05-07 Christopher Eckner , Noemi Anau Montel , Florian List , Francesca Calore , Christoph Weniger

A fundamental problem of cosmic ray (CR) physics is the determination of the average properties of Galactic CRs outside the Solar system. Starting from COS-B data in the 1980's, gamma-ray observations of molecular clouds in the Gould Belt…

High Energy Astrophysical Phenomena · Physics 2015-06-05 M. Kachelriess , S. Ostapchenko

We show that the complex shape of the cosmic ray (CR) spectrum, as recently measured by PAMELA and inferred from Fermi-LAT gamma-ray observations of molecular clouds in the Gould belt, can be naturally understood in terms of basic plasma…

High Energy Astrophysical Phenomena · Physics 2012-08-10 Pasquale Blasi , Elena Amato , Pasquale D. Serpico

We introduce a novel diffusion model for the propagation of cosmic rays (CRs) that incorporates an anisotropic diffusion tensor of a general form within a realistically modeled large-scale Galactic magnetic field. The parameters of the…

High Energy Astrophysical Phenomena · Physics 2025-07-22 V. D. Borisov , V. O. Yurovsky , I. A. Kudryashov

Radio-loud active galactic nuclei (AGN) are expected to contribute substantially to both the intensity and anisotropy of the isotropic gamma-ray background (IGRB). In turn, the measured properties of the IGRB can be used to constrain the…

High Energy Astrophysical Phenomena · Physics 2014-12-03 Mattia Di Mauro , Alessandro Cuoco , Fiorenza Donato , Jennifer M. Siegal-Gaskins

We present the analysis of 9.7 years Fermi-LAT data of the middle-aged supernova remnant W44 and the massive molecular gas complex that surrounds it. We derived a high-quality spectral energy distribution of gamma-radiation of the shell…

High Energy Astrophysical Phenomena · Physics 2020-07-10 Giada Peron , Felix Aharonian , Sabrina Casanova , Roberta Zanin , Carlo Romoli

Motivated by the discovery of the non-thermal Fermi bubble features both below and above the Galactic plane, we investigate a scenario in which these bubbles are formed through Galacto-centric outflow. Cosmic rays (CR) both diffusing and…

High Energy Astrophysical Phenomena · Physics 2017-01-11 Andrew M. Taylor , Gwenael Giacinti

We present the implementation and the first results of cosmic ray (CR) feedback in the Feedback In Realistic Environments (FIRE) simulations. We investigate CR feedback in non-cosmological simulations of dwarf, sub-$L\star$ starburst, and…

Astrophysics of Galaxies · Physics 2019-09-04 T. K. Chan , D. Keres , P. F. Hopkins , E. Quataert , K. -Y. Su , C. C. Hayward , C. -A. Faucher-Giguere

The diffuse gamma ray emission from astrophysical backgrounds in our Galaxy and the signal due to the annihilation or decay of Dark Matter (DM) in the Galactic Halo are expected to have a substantially different morphology and spectral…

High Energy Astrophysical Phenomena · Physics 2019-08-14 Gabrijela Zaharijas , Alessandro Cuoco , Zhaoyu Yang , Jan Conrad

During its first year of data taking, the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope has collected a large sample of high-energy cosmic-ray electrons and positrons (CREs). We present the results of a directional…

High Energy Astrophysical Phenomena · Physics 2015-05-28 The Fermi LAT Collaboration

Recently evidence has emerged for enormous features in the gamma-ray sky observed by the Fermi-LAT instrument: bilateral `bubbles' of emission centered on the core of the Galaxy and extending to around 10 kpc above and below the Galactic…

Astrophysics of Galaxies · Physics 2011-03-24 Roland M. Crocker , Felix Aharonian

In this paper, we analyzed 12 years of Fermi LAT gamma-ray data towards three nearby giant molecular clouds (GMCs), i.e., R~CrA, Chamaeleon, and Lupus. We calibrated the gas column density of these regions by using the Planck dust opacity…

High Energy Astrophysical Phenomena · Physics 2023-04-28 Jiahao Liu , Bing Liu , Ruizhi Yang

One of the unsolved problems in cosmic ray (CR) physics is the small radial gradient of the gamma-ray intensity compared to the inferred CR source distribution in the Galactic disk. In diffusive CR propagation models the most natural…

Astrophysics · Physics 2007-05-23 D. Breitschwerdt , V. Dogiel , H. J. V"olk

For over 15 years the Fermi Large Area Telescope (Fermi-LAT) has been monitoring the entire high-energy gamma-ray sky, providing the best sampled 0.1 -- $>1$ TeV photons to this day. As a result, the Fermi-LAT has been serving the…

High Energy Astrophysical Phenomena · Physics 2023-08-25 Janeth Valverde , D. Kocevski , M. Negro , S. Garrappa , A. Brill

Radially inhomogeneous gamma-ray burst (GRB) jets release variable photospheric emission and can have internal shocks occurring above the photosphere. We generically formulate a photospheric emission model of GRBs including Compton…

High Energy Astrophysical Phenomena · Physics 2015-05-18 Kenji Toma , Xue-Feng Wu , Peter Meszaros

In over two years of operation Fermi-LAT has revolutionized our knowledge of the gamma-ray sky. Interstellar gamma rays are part of this new era and allow unprecedented tests for models of cosmic rays in the Galaxy. The extension to lower…

High Energy Astrophysical Phenomena · Physics 2017-08-23 A. W. Strong

Employing data collected during the first 25 months' observations by the Fermi-LAT, we describe and subsequently seek to model the very high energy (>300 MeV) emission from the central few parsecs of our Galaxy. We analyze the…

High Energy Astrophysical Phenomena · Physics 2011-09-08 M. Chernyakova , D. Malyshev , F. A. Aharonian , R. M. Crocker , D. I. Jones

We perform a detailed study of the sensitivity to the anisotropies related to Dark Matter (DM) annihilation in the Isotropic Gamma-Ray Background (IGRB) as measured by the Fermi Large Area Telescope (Fermi-LAT). For the first time, we take…

High Energy Astrophysical Phenomena · Physics 2011-09-07 A. Cuoco , A. Sellerholm , J. Conrad , S. Hannestad

We conducted an analysis of gamma-ray variability in a large sample of jetted active galactic nuclei (AGNs) by utilizing archival Fermi-LAT light curves and applying damped random walk modeling to obtain variability amplitude. Our primary…

High Energy Astrophysical Phenomena · Physics 2026-05-21 Yongyun Chen , Qiusheng Gu , Junhui Fan , Dingrong Xiong , Xiaoling Yu , Xiaogu Zhong , Xiaotong Guo , Nan Ding