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We study the link between galaxies and HI-selected absorption systems at z~3-4 in the MUSE Analysis of Gas around Galaxies (MAGG) survey, an ESO large programme consisting of integral field pectroscopic observations of 28 quasar fields…

We analyze $Chandra$ observations of the hot atmospheres of 40 early spiral and elliptical galaxies. Using new temperature, density, cooling time, and mass profiles, we explore relationships between their hot atmospheres and cold molecular…

Astrophysics of Galaxies · Physics 2020-01-08 Iu. V. Babyk , B. R. McNamara , P. D. Tamhane , P. E. J. Nulsen , H. R. Russell , A. C. Edge

The observed spectral bump in cosmic-ray (CR) proton and helium spectra, along with the phase and amplitude evolution of CR dipole anisotropy, provide plausible yet indirect evidence for the presence of a nearby CR source. This study…

High Energy Astrophysical Phenomena · Physics 2025-06-25 Xing-Jian Lv , Xiao-Jun Bi , Kun Fang , Peng-Fei Yin , Meng-Jie Zhao

The origin of the diffuse extragalactic, high-energy gamma-ray background (EGRB) filling the Universe remains unknown. The spectrum of this extragalactic radiation, as measured by the EGRET on-board CGRO, is well-fit by a power law across…

Astrophysics · Physics 2009-11-07 Caleb A. Scharf , Reshmi Mukherjee

Recent evidence for a large Galactic halo, based on cosmic-ray radioactive nuclei, implies a significant contribution from inverse Compton emission at high Galactic latitudes. We present predictions for the expected intensity distribution,…

Astrophysics · Physics 2007-05-23 A. W. Strong , I. V. Moskalenko , O. Reimer

The data from the Nobeyama Radio Observatory 45 m telescope Galactic Center CO survey have been analyzed to generate a compilation of molecular clouds with intense CO emission in this region. Clouds are identified in an automated manner…

Astrophysics · Physics 2009-10-31 T. Oka , T. Hasegawa , F. Sato , M. Tsuboi , A. Miyazaki

We present the germ of a new model for High Velocity Clouds, derived from the idea that the dark matter halo of our Galaxy is in the form of cold, planetary-mass gas clouds. In this picture HVCs arise as a result of disruptive collisions…

Astrophysics · Physics 2007-05-23 Mark Walker , Mark Wardle

From astronomical observations, we know that dark matter exists and makes up $\sim$25\% of our Universe. Recently the study of anomalous gamma-ray emission in the regions surrounding the galactic center has drawn a lot of attention. It has…

High Energy Physics - Phenomenology · Physics 2015-07-08 Tanmoy Mondal , Tanushree Basak

(ABRIDGED) The Gamma-ray Large Area Space Telescope (GLAST) will measure the spectra of distant extragalactic sources of high energy gamma-rays. GLAST can look for energy dependent propagation effects from such sources as a signal of…

Astrophysics · Physics 2008-11-26 F. W. Stecker

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

Various theoretical models predict the existence of extended $\gamma$-ray halo around normal galaxies that could be produced by interactions of cosmic rays with the circumgalactic medium or by annihilation or decay of hypothetical dark…

High Energy Astrophysical Phenomena · Physics 2026-04-03 M. S. Pshirkov , B. A. Nizamov

Recent observations of gamma-rays with the Fermi Large Area Telescope (LAT) in the direction of the inner Galaxy revealed a mysterious GeV excess. Its intensity is significantly above predictions of the standard model of cosmic rays (CRs)…

High Energy Astrophysical Phenomena · Physics 2021-08-10 Dmitry O. Chernyshov , Andrei E. Egorov , Vladimir A. Dogiel , Alexei V. Ivlev

Young energetic pulsars will likely be the largest class of Galactic sources observed by GLAST, with many hundreds detected. Many will be unknown as radio pulsars, making pulsation detection dependent on radio and/or x-ray observations or…

Astrophysics · Physics 2009-06-23 Scott M. Ransom

We describe a catalogue of gamma-ray source candidates, selected using the Minimum Spanning Tree (MST) algorithm on the 9-years Fermi-LAT sky (Pass 8) at energies higher than 10 GeV. The extragalactic sky at absolute Galactic latitudes…

High Energy Astrophysical Phenomena · Physics 2018-10-31 R. Campana , E. Massaro , E. Bernieri

Until now the known sources in the Galactic center with sufficiently smooth spectra and of sufficient brightness to be suitable for high resolution infrared absorption spectroscopy of interstellar gas occupied a narrow range of longitudes,…

Astrophysics of Galaxies · Physics 2015-05-14 T. R. Geballe , T. Oka

The fast temporal structures and cosmological distances of gamma-ray bursts (GRBs) afford a natural laboratory for testing theories of frequency-dependent propagation of high-energy photons, as predicted for quantum gravity (QG). We…

Astrophysics · Physics 2007-05-23 J. P. Norris , J. T. Bonnell , G. F. Marani , J. D. Scargle

The Gamma-ray Large Area Space Telescope (GLAST) is an observatory designed to perform gamma-ray astronomy in the energy range 20 MeV to 300 GeV, with supporting measurements for gamma-ray bursts from 10 keV to 25 MeV. GLAST will be…

Astrophysics · Physics 2009-06-23 D. Paneque , A. Borgland , A. Bovier , E. Bloom , Y. Edmonds , S. Funk , G. Godfrey , R. Rando , L. Wai , P. Wang

A subset of the unidentified EGRET gamma-ray sources with no active galactic nucleus or other conspicuous counterpart appears to be concentrated at medium latitudes. Their long-term variability and their spatial distribution indicate that…

Astrophysics · Physics 2009-11-10 I. A. Grenier , M. M. Kaufman Bernado , G. E. Romero

High velocity gas that does not conform to Galactic rotation is observed throughout the Galaxy's halo. One component of this gas, HI high velocity clouds (HVCs), have attracted attention since their discovery in the 1960s and remain…

Astrophysics of Galaxies · Physics 2017-08-24 Asger Grønnow , Thor Tepper-García , Joss Bland-Hawthorn , Naomi McClure-Griffiths

We present a model for the interpretation of the gamma-ray background emission from the Galactic halo, which we attribute to interaction of high-energy cosmic rays with dense molecular clumps. In a wide range of clump parameters we…

Astrophysics · Physics 2007-05-23 P. M. W. Kalberla , Yu. A. Shchekinov , R. -J. Dettmar
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