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The Fermi LAT has opened the way for comparative studies of cosmic rays (CRs) and high-energy objects in the Milky Way (MW) and in other, external, star-forming galaxies. Using 2 yr of observations with the Fermi LAT, local Group galaxy M31…

High Energy Astrophysical Phenomena · Physics 2017-03-01 LAT Collaboration

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

In this work, we revisit the all-sky Galactic diffuse $\gamma$-ray emission taking into account the new measurements of cosmic ray electron/positron spectrum by PAMELA, ATIC and Fermi, which show excesses of cosmic electrons/positrons…

High Energy Astrophysical Phenomena · Physics 2014-11-20 Juan Zhang , Qiang Yuan , Xiao-Jun Bi

We compare the surface brightness profile and morphology of the Galactic Centre Excess (GCE) identified in wide-angle $\gamma$-ray maps from the Fermi-Large Area Telescope to dark matter annihilation predictions derived from high-resolution…

Cosmology and Nongalactic Astrophysics · Physics 2022-02-09 Robert J. J. Grand , Simon D. M. White

Two unresolved questions at galaxy centers, namely the formation of the nuclear star cluster (NSC) and the origin of the gamma-ray excess in the Milky Way (MW) and Andromeda (M31), are both related to the formation and evolution of globular…

Astrophysics of Galaxies · Physics 2023-12-27 Yuan Gao , Hui Li , Xiaojia Zhang , Meng Su , Stephen Chi Yung Ng

Nearby clusters and groups of galaxies are potentially bright sources of high-energy gamma-ray emission resulting from the pair-annihilation of dark matter particles. However, no significant gamma-ray emission has been detected so far from…

Cosmology and Nongalactic Astrophysics · Physics 2010-05-25 LAT Collaboration

Recently, a spatially extended excess of gamma rays collected by the Fermi-LAT from the inner region of the Milky Way has been detected by different groups and with increasingly sophisticated techniques. Yet, any final conclusion about the…

High Energy Astrophysical Phenomena · Physics 2015-02-11 Francesca Calore , Ilias Cholis , Christoph Weniger

The nearby Large Magellanic Cloud (LMC) provides a rare opportunity of a spatially resolved view of an external star-forming galaxy in gamma-rays. The LMC was detected at 0.1-100GeV as an extended source with CGRO/EGRET and using early…

High Energy Astrophysical Phenomena · Physics 2015-11-09 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

We analyze the processes governing cosmic-ray (CR) penetration into molecular clouds and the resulting generation of gamma-ray emission. The density of CRs inside a cloud is depleted at lower energies due to the self-excited MHD turbulence.…

High Energy Astrophysical Phenomena · Physics 2018-12-05 V. A. Dogiel , D. O. Chernyshov , A. V. Ivlev , D. Malyshev , A. W. Strong , K. S. Cheng

We have modelled the high-energy astrophysics of the inner 200 pc of the Galaxy with a view to explaining the diffuse, broad-band (radio continuum to TeV gamma-ray), non-thermal signal detected from this region. Our modelling pins down the…

High Energy Astrophysical Phenomena · Physics 2011-03-29 Roland M. Crocker

Recently, a preliminary spectrum from the Fermi Gamma-ray Space Telescope has been presented for the inner galaxy (-30 < l < 30, -5 < b < 5), as well as the galactic center (-1 < l < 1, -1< b < 1). We consider the implications of these data…

High Energy Astrophysical Phenomena · Physics 2009-07-29 Ilias Cholis , Gregory Dobler , Douglas P. Finkbeiner , Lisa Goodenough , Tracy R. Slatyer , Neal Weiner

We present a new method to interpret the $\gamma$-ray data of our inner Galaxy as measured by the Fermi Large Area Telescope (Fermi LAT). We train and test convolutional neural networks with simulated Fermi-LAT images based on models tuned…

High Energy Astrophysical Phenomena · Physics 2018-05-29 Sascha Caron , Germán A. Gómez-Vargas , Luc Hendriks , Roberto Ruiz de Austri

We present evidence for $\gamma$-ray emission from a stacked population of 39 high-latitude globular clusters (GCs) not detected in the Fermi Point Source Catalog, likely attributable to populations of millisecond pulsars within them. In…

High Energy Astrophysical Phenomena · Physics 2024-10-17 Owen K. Henry , Timothy A. D. Paglione , Yuzhe Song , Joshua Tan , David Zurek , Vanessa Pinto

The origin of Galactic cosmic rays (with energies up to 10^15 eV) remains unclear, though it is widely believed that they originate in the shock waves of expanding supernova remnants. Currently the best way to investigate their acceleration…

Astrophysics · Physics 2012-08-27 The H. E. S. S. Collaboration , : , F. A. Aharonian

The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope provides both direct and indirect measurements of Galactic cosmic rays (CR). The LAT high-statistics observations of the 7 GeV - 1 TeV electron plus positron spectrum and…

High Energy Astrophysical Phenomena · Physics 2015-03-19 David J. Thompson , Luca Baldini , Yasunobu Uchiyama

The density of cosmic rays inside molecular clouds determines the ionization rate in the dense cores where stars form. It is also one of the drivers of astrochemistry leading to the creation of complex molecules. Through Fermi Large Area…

High Energy Astrophysical Phenomena · Physics 2023-01-18 Rui-zhi Yang , Guang-Xing Li , Emma de Oña Wilhelmi , Yu-Dong Cui , Bing Liu , Felix Aharonian

It has been proposed that a recent outburst of cosmic-ray electrons could account for the excess of GeV-scale gamma rays observed from the region surrounding the Galactic Center. After studying this possibility in some detail, we identify…

High Energy Astrophysical Phenomena · Physics 2015-12-09 Ilias Cholis , Carmelo Evoli , Francesca Calore , Tim Linden , Christoph Weniger , Dan Hooper

We analyze the first two years of data from the Fermi Gamma Ray Space Telescope from the direction of the inner 10 degrees around the Galactic Center with the intention of constraining, or finding evidence of, annihilating dark matter. We…

High Energy Physics - Phenomenology · Physics 2015-03-17 Dan Hooper , Lisa Goodenough

The $Fermi$ gamma-ray telescope discovered a pair of bubbles at the Galactic center. These structures are spatially-correlated with the microwave emission detected by the WMAP and Planck satellites. These bubbles were likely inflated by a…

High Energy Astrophysical Phenomena · Physics 2015-06-18 M. Ruszkowski , H. -Y. K. Yang , E. Zweibel