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Apart from the Milky Way, the Large Magellanic Cloud (LMC) is the only other normal star-forming galaxy that was conclusively detected in high energy (> 100 MeV) gamma rays by the Energetic Gamma Ray Telescope (EGRET) on the Compton…

High Energy Astrophysical Phenomena · Physics 2019-08-13 T. A. Porter , J. Knodlseder

Within the classical convection--diffusion approximation, we show that the angular distribution of cosmic rays (CRs) in a highly turbulent flow may exhibit significant small-scale anisotropies. The CR intensity angular power spectrum $…

High Energy Astrophysical Phenomena · Physics 2024-02-27 Yiran Zhang , Siming Liu

Star formation in galaxies is observed to be associated with gamma-ray emission. The detection of gamma rays from star-forming galaxies by the Fermi Large Area Telescope (LAT) has allowed the determination of a functional relationship…

High Energy Astrophysical Phenomena · Physics 2012-08-07 Emma Storm , Tesla E. Jeltema , Stefano Profumo

Determining the spatial distribution of Galactic cosmic rays (CRs) is fundamental to understand how these particles propagate in interstellar space and to infer their source spectra. The most sensitive method of studying this problem is…

High Energy Astrophysical Phenomena · Physics 2025-09-26 Paolo Lipari , Silvia Vernetto

With its excellent sensitivity, large field of view, broad energy coverage, and good per-photon angular resolution, the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope satellite provides us with an unprecedented view of the…

High Energy Astrophysical Phenomena · Physics 2022-03-02 Jürgen Knödlseder

The anisotropy of cosmic rays (CRs) in the solar vicinity is generally at- tributed to the CR streaming due to the discrete distribution of CR sources or local magnetic field modulation. Recently, the two dimensional large scale CR…

Astrophysics of Galaxies · Physics 2012-04-17 Xiao-bo Qu , Yi Zhang , Liang Xue , Cheng Liu , Hong-bo Hu

We present a new analysis of cosmic dipole anisotropy using gamma-ray bursts (GRBs) as high-redshift standardizable candles. GRBs are ideal probes for testing the cosmological principle thanks to their high luminosity, wide redshift range,…

Cosmology and Nongalactic Astrophysics · Physics 2026-03-25 Jessica Santiago , Kerkyra Asvesta , Maria Giovanna Dainotti , Pisin Chen

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

Recent observations of cosmic rays (CRs) have revealed a two-component anomaly in the spectra of primary and secondary particles, as well as their ratios, prompting investigation into their common origin. In this study, we incorporate the…

High Energy Astrophysical Phenomena · Physics 2024-03-08 Yu-Hua Yao , Xu-Lin Dong , Yi-Qing Guo , Qiang Yuan

Theories of galaxy formation predict the existence of extended gas halo around spiral galaxies. If there are 10-100 nG magnetic fields at several ten kpc distances from the galaxies, extended galactic cosmic ray (CR) haloes could also…

Astrophysics of Galaxies · Physics 2016-01-01 M. S. Pshirkov , V. V. Vasiliev , K. A. Postnov

Many galaxy clusters have giant halos of non-thermal radio emission, indicating the presence of relativistic electrons in the clusters. Relativistic protons may also be accelerated by merger and/or accretion shocks in galaxy clusters. These…

High Energy Astrophysical Phenomena · Physics 2018-09-19 Shao-Qiang Xi , Xiang-Yu Wang , Yun-Feng Liang , Fang-Kun Peng , Rui-Zhi Yang , Ruo-Yu Liu

We study the spectral properties of the cosmic-ray spectrum in the interstellar medium within 1 kpc distance from the Sun. We used eight-year exposure data of molecular clouds of the Gould Belt obtained with the Fermi/LAT telescope to…

High Energy Astrophysical Phenomena · Physics 2017-10-04 Andrii Neronov , Denys Malyshev , Dmitri V. Semikoz

Recent cosmic ray (CR) measurements have revealed unexpected anomalies in secondary CRs, namely deviations from the predictions of the so-called standard Galactic CR paradigm regarding the composition and energy spectra of the products of…

High Energy Astrophysical Phenomena · Physics 2024-10-30 Rui-zhi Yang , Felix Aharonian

Recently, the {\it{Fermi}} space telescope has discovered two large $\gamma$-ray emission regions, the so-called "Fermi bubbles", that extend up to $\sim 50^\circ$ above and below the Galactic center. The $\gamma$-ray emission from the…

High Energy Astrophysical Phenomena · Physics 2015-06-15 Satyendra Thoudam

The inner region of the Milky Way is one of the most interesting and complex regions of the gamma-ray sky. The intense interstellar emission and resolved point sources, as well as potential contributions by other sources such as unresolved…

High Energy Astrophysical Phenomena · Physics 2019-08-13 Troy A. Porter , Simona Murgia

We report an analysis of the interstellar gamma-ray emission from the Chamaeleon, R Coronae Australis (R CrA), and Cepheus and Polaris flare regions with the Fermi Large Area Telescope. They are among the nearest molecular cloud complexes,…

High Energy Astrophysical Phenomena · Physics 2017-02-22 LAT collaboration

The total anisotropy of a diffuse background composed of two or more sources, such as the Fermi-LAT--measured gamma-ray background, is set by the anisotropy of each source population and the contribution of each population to the total…

Cosmology and Nongalactic Astrophysics · Physics 2013-08-14 Brandon S. Hensley , Vasiliki Pavlidou , Jennifer M. Siegal-Gaskins

It has been shown that supernova blast waves interacting with winds from massive stars in compact star clusters may be capable of producing cosmic-ray (CR) protons to above $10^{17}$ eV. We give a brief description of the…

High Energy Astrophysical Phenomena · Physics 2019-12-13 A. M. Bykov , M. E. Kalyashova , D. C. Ellison , S. M. Osipov

With the discovery of high energy {\gamma}-ray emission from the Andromeda galaxy (M 31) by the Fermi/LAT collaboration, normal galaxies begin to arise from the shadows for the first time, providing insight on cosmic ray acceleration in…

High Energy Astrophysical Phenomena · Physics 2011-09-22 Jean-Philippe Lenain , Roland Walter

Axion-like particles (ALPs) may be abundantly produced in core-collapse (CC) supernovae (SNe), hence the cumulative signal from all past SN events can create a diffuse flux peaked at energies of about 25~MeV. We improve upon the modeling of…

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