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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

The $\gamma$-ray observation of interstellar gas provides a unique way to probe the cosmic rays (CRs) outside the solar system. In this work, we use an updated version of Fermi-LAT data and recent multi-wavelength tracers of interstellar…

High Energy Astrophysical Phenomena · Physics 2019-06-19 Zhao-Qiang Shen , Xiaoyuan Huang , Qiang Yuan , Yi-Zhong Fan , Da-Ming Wei

Cosmic rays (CRs) are ubiquitous in the interstellar medium (ISM) of nearby galaxies, but many of their properties are not well-constrained. Gamma-ray observations provide a powerful tool in this respect, allowing us to constrain both the…

High Energy Astrophysical Phenomena · Physics 2023-07-19 Maria Werhahn , Philipp Girichidis , Christoph Pfrommer , Joseph Whittingham

It is widely accepted that cosmic rays (CRs) up to at least PeV energies are Galactic in origin. Accelerated particles are injected into the interstellar medium where they propagate to the farthest reaches of the Milky Way, including a…

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

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

Cosmic rays (CRs) interact with the gas, the radiation field and the magnetic field in the Milky Way, producing diffuse emission from radio to gamma rays. Observations of this diffuse emission and comparison with detailed predictions are…

After the discovery of Fermi Bubbles and the excess of gamma-ray emission, the Galactic Centre has received increasing attention with the aim to understand its role in the origin and acceleration of primary cosmic rays (CRs). Based on a…

High Energy Astrophysical Phenomena · Physics 2020-06-15 Rita C. Anjos , Fernando Catalani

Various studies have implied the existence of a gaseous halo around the Galaxy extending out to 100 kpc. Galactic cosmic rays (CRs) that propagate to the halo, either by diffusion or by convection with the possibly existing large-scale…

High Energy Astrophysical Phenomena · Physics 2019-01-30 Ruo-Yu Liu , Huirong Yan , Xiang-Yu Wang , Shi Shao , Hui Li

High-energy gamma rays of interstellar origin are produced by the interaction of cosmic-ray (CR) particles with the diffuse gas and radiation fields in the Galaxy. The main features of this emission are well understood and are reproduced by…

High Energy Astrophysical Phenomena · Physics 2017-09-06 Troy A. Porter , Gudlaugur Johannesson , Igor V. Moskalenko

The standard approach to cosmic-ray (CR) propagation in the Galaxy is based on the assumption that local transport properties can be extrapolated to the whole CR confining volume. Such models tend to underestimate the gamma-ray flux above…

High Energy Astrophysical Phenomena · Physics 2015-05-06 Daniele Gaggero , Alfredo Urbano , Mauro Valli , Piero Ullio

Recent data from ATIC, CREAM and PAMELA indicate that the cosmic ray energy spectra of protons and nuclei exhibit a remarkable hardening at energies above 100 GeV per nucleon. We propose that the hardening is an interstellar propagation…

High Energy Astrophysical Phenomena · Physics 2012-05-29 N. Tomassetti

Observations of diffuse Galactic gamma-ray spectrum by the EGRET instrument reveal an excess above ~ 1 GeV over the expected gamma-ray spectrum calculated under the assumption that the locally observed cosmic-ray (CR) spectra represent the…

Astrophysics · Physics 2009-11-11 Thoudam Satyendra

We consider the problem of the cosmic ray spectrum formation assuming that cosmic rays are produced by Galactic sources. The anomalous diffusion equation proposed in our recent papers is used to describe cosmic ray propagation in the…

High Energy Astrophysical Phenomena · Physics 2019-05-17 Nikolay Volkov , Anatoly Lagutin , Alexander Tyumentsev , Roman Raikin

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

Gamma-ray emission produced by interactions between cosmic rays (CRs) and interstellar gas traces the product of their densities throughout the Milky Way. The outer Galaxy is a privileged target of investigation to separate interstellar…

High Energy Astrophysical Phenomena · Physics 2019-08-13 Luigi Tibaldo , Isabelle A. Grenier , Tsunefumi Mizuno

The Galactic diffuse soft gamma-ray (30-800 keV) emission has been measured from the Galactic Center by the HIREGS balloon-borne germanium spectrometer to determine the spectral characteristics and origin of the emission. The resulting…

Astrophysics · Physics 2009-10-31 S. E. Boggs , R. P. Lin , S. Slassi-Sennou , W. Coburn , R. M. Pelling

We have developed a model which aims to reproduce observational data of many kinds related to cosmic-ray origin and propagation: direct measurements of nuclei, antiprotons, electrons and positrons, gamma-rays, and synchrotron radiation. Our…

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

A new calculation of the Galactic diffuse gamma-ray spectrum from the decay of secondary particles produced by interactions of cosmic-ray protons with interstellar matter is presented. The calculation utilizes the modern Monte Carlo event…

Astrophysics · Physics 2009-10-28 Masaki Mori