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From the analysis of AGASA data above $4 \times 10^{19}$ eV, we show that the ultra-high energy cosmic rays flux is neither purely isotropic, nor reflects the expected anisotropy from a pure source distribution that maps large scale…

Astrophysics · Physics 2009-10-31 Gustavo Medina-Tanco

Motivated by the PAMELA anomaly in the fluxes of cosmic-ray positron and electron, we study the cosmic gamma-ray induced by the inverse Compton (IC) scattering process in unstable dark matter scenario assuming that the anomaly is due to the…

High Energy Physics - Phenomenology · Physics 2015-05-14 Koji Ishiwata , Shigeki Matsumoto , Takeo Moroi

Here is reviewed our current understanding of Galactic and extragalactic diffuse gamma-ray emission. The spectrum of the extragalactic gamma-ray background above 30 MeV can be well described by a power law with photon index s=2.1. In the…

Astrophysics · Physics 2007-05-23 Martin Pohl

Dark matter annihilating in our Galaxy's halo and elsewhere in the universe is expected to generate a diffuse flux of gamma rays, potentially observable with next generation satellite-based experiments, such as GLAST. In this article, we…

Astrophysics · Physics 2009-11-13 Dan Hooper , Pasquale D. Serpico

Dark matter annihilation in Galactic substructure produces diffuse gamma-ray emission of remarkably constant intensity across the sky, and in general this signal dominates over the smooth halo signal at angles greater than a few tens of…

High Energy Astrophysical Phenomena · Physics 2009-07-02 Jennifer M. Siegal-Gaskins

Deviations from isotropy have been a key tool to identify the sources and the primary type of cosmic rays (CRs) at low energies. We argue that anisotropies due to blind regions induced by the Galactic magnetic field, the cosmological…

Astrophysics · Physics 2008-11-26 M. Kachelriess

Annihilating dark matter particles produce roughly as much power in electrons and positrons as in gamma ray photons. The charged particles lose essentially all of their energy to inverse Compton and synchrotron processes in the galactic…

Astrophysics · Physics 2009-11-10 E. A. Baltz , L. Wai

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

The existence of the cosmic ray Halo in our Galaxy has been discussed for more than half a century. If it is real it could help to explain some puzzling features of the cosmic ray flux: its small radial gradient, nearly perfect isotropy and…

Astrophysics of Galaxies · Physics 2015-06-19 Anatoly Erlykin , Arnold Wolfendale

We obtain the dipolar anisotropies in the arrival directions of ultra-high energy cosmic rays diffusing from nearby extragalactic sources. We discuss both the energy regime of spatial diffusion and the quasi-rectilinear one leading to just…

High Energy Astrophysical Phenomena · Physics 2014-06-11 Diego Harari , Silvia Mollerach , Esteban Roulet

The universe is filled with a diffuse and isotropic extragalactic background of gamma-ray radiation, containing roughly equal energy flux per decade in photon energy between 3 MeV-100 GeV. The origin of this background is one of the…

Astrophysics · Physics 2011-05-05 Abraham Loeb , Eli Waxman

Recently the AGASA Collaboration presented data suggesting a significant clustering of ultra-high energy cosmic rays coming from the outer Galaxy region. In this paper we calculate expected cosmic ray arrival distributions for several…

Astrophysics · Physics 2011-05-12 Jaime Alvarez-Muñiz , Ralph Engel , Todor Stanev

The intergalactic magnetic field (IGMF) may leave an imprint on the angular anisotropy of the extragalactic gamma-ray background through its effect on electromagnetic cascades triggered by interactions between very high energy photons and…

High Energy Astrophysical Phenomena · Physics 2015-06-03 Tonia M. Venters , Vasiliki Pavlidou

The problem of the origin of cosmic rays in the shocks produced by supernova explosions at energies below the so called 'knee' (at ~3*10$^6$ GeV) in the energy spectrum is addressed, with special attention to the propagation of the…

Astrophysics · Physics 2008-11-26 A. D. Erlykin , A. A. Lagutin , A. W. Wolfendale

The spectral distortion of the cosmic background radiation produced by the inverse Compton scattering on hot electrons in clusters of galaxies (thermal Sunyaev-Zeldovich effect) is calculated for arbitrary optical depth and electron…

Astrophysics · Physics 2009-10-31 A. D. Dolgov , S. H. Hansen , S. Pastor , D. V. Semikoz

Recent studies suggest that the anisotropy in cosmic-ray arrival directions can provide insight into local acceleration sites and propagation conditions. We developed a unified framework to interpret both the observed energy spectra and the…

High Energy Astrophysical Phenomena · Physics 2025-11-25 Bing-qiang Qiao , Wei Liu , Huirong Yan , Yi-qing Guo

We present quantitative statistical evidence for a $\gamma$-ray emission halo surrounding the Galaxy. Maps of the emission are derived. EGRET data were analyzed in a wavelet-based non-parametric hypothesis testing framework, using a model…

Analyses of measurements of the distribution of absolute brightness temperature over the radio sky have led recently to suggestions that there exists a substantial unexplained extragalactic radio background. Consequently, there have been…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-16 Ravi Subrahmanyan , Ramanath Cowsik

Gamma-ray binaries, composed of a massive star and compact object, have been established as a new class of sources of very high energy (VHE) photons. The gamma-rays are produced by inverse Compton scattering of the stellar light by VHE…

Astrophysics · Physics 2008-11-26 G. Dubus , B. Cerutti , G. Henri

The backward Compton scattering is a basic process at future higher energy photon colliders. To obtain a high probability of e->gamma conversion the density of laser photons in the conversion region should be so high that simultaneous…

High Energy Physics - Phenomenology · Physics 2008-11-26 M. Galynskii , E. Kuraev , M. Levchuk , V. Telnov