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Low-energy (~MeV) cosmic rays (CRs) ionize molecular clouds and create the neutral iron line (Fe I K\alpha) at 6.4 keV. On the other hand, high-energy (>~ GeV) CRs interact with the dense cloud gas and produce gamma rays. Based on a…

High Energy Astrophysical Phenomena · Physics 2021-02-22 Yutaka Fujita , Kumiko K. Nobukawa , Hidetoshi Sano

We investigate the impact of cosmic rays (CRs) on galactic outflows from a multi-phase interstellar medium with solar neighbourhood conditions. The three-dimensional magneto-hydrodynamical simulations include CRs as a relativistic fluid in…

Astrophysics of Galaxies · Physics 2018-07-11 Philipp Girichidis , Thorsten Naab , Michał Hanasz , Stefanie Walch

We investigate the dynamical interaction between cosmic rays (CRs) and the multiphase interstellar medium (ISM) using numerical magnetohydrodynamic (MHD) simulations with a two-moment CR solver and TIGRESS simulations of star-forming…

Astrophysics of Galaxies · Physics 2024-01-10 Lucia Armillotta , Eve C. Ostriker , Chang-Goo Kim , Yan-Fei Jiang

The energy spectrum of electrons produced in molecular gas by interstellar cosmic rays (CRs) is rigorously calculated as a function of gas column density $N$ traversed by the CRs. This allows us to accurately compute the local value of the…

Astrophysics of Galaxies · Physics 2021-03-17 Alexei V. Ivlev , Kedron Silsbee , Marco Padovani , Daniele Galli

The specific star-formation rate of star-forming `main sequence' galaxies significantly decreased since z~1.5, due to the decreasing molecular gas fraction and star formation efficiency. However, the radio-infrared (IR) correlation has not…

Astrophysics of Galaxies · Physics 2025-01-29 B. Vollmer , J. Freundlich , P. Gratier , Th. Lizee , M. Lendrin , J. Braine , M. Soida

We study heating of cool cores in galaxy clusters by cosmic-ray (CR) streaming using numerical simulations. In this model, CRs are injected by the central active galactic nucleus (AGN) and move outward with Alfven waves. The waves are…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-28 Yutaka Fujita , Yutaka Ohira

Understanding cosmic ray (CR) diffusion in a partially ionized medium is both crucial and challenging. In this study, we investigate CR perpendicular superdiffusion and parallel transport in turbulent, partially ionized media using…

Astrophysics of Galaxies · Physics 2025-10-09 Yue Hu , Siyao Xu , Alex Lazarian , James M. Stone , Philip F. Hopkins

One of the unsolved problems in cosmic ray (CR) physics is the small radial gradient of the gamma-ray intensity compared to the inferred CR source distribution in the Galactic disk. In diffusive CR propagation models the most natural…

Astrophysics · Physics 2007-05-23 D. Breitschwerdt , V. Dogiel , H. J. V"olk

The $\gamma$-ray emission of star-forming (SF) galaxies is attributed to hadronic interactions of cosmic ray (CR) protons with the interstellar gas and contributions from CR electrons via bremsstrahlung and inverse Compton (IC) scattering.…

High Energy Astrophysical Phenomena · Physics 2021-05-26 Maria Werhahn , Christoph Pfrommer , Philipp Girichidis , Georg Winner

Cosmic rays (CRs) streaming in weakly magnetized plasmas can drive large-amplitude magnetic fluctuations via nonresonant streaming instability (NRSI), or Bell instability. Using one-dimensional kinetic simulations, we investigate how…

High Energy Astrophysical Phenomena · Physics 2025-11-27 Saikat Das , Siddhartha Gupta , Prateek Sharma

Spectrum and chemical composition of cosmic rays accelerated in supernova remnants are studied on a basis of kinetic approach. The cosmic ray transport equation with the Bohm diffusion coefficient has been numerically solved…

Astrophysics · Physics 2008-02-03 E. G. Berezhko , G. F. Krymsky , V. K. Yelshin , L. T. Ksenofontov

Recent gamma-ray observations reveal inhomogeneous diffusion of cosmic rays (CRs) in the interstellar medium (ISM). This is expected as the diffusion of CRs depends on the properties of turbulence, which can vary widely in the multi-phase…

High Energy Astrophysical Phenomena · Physics 2021-12-15 Siyao Xu

Cosmic rays (CRs) are thought to play a dynamically important role in several key aspects of galaxy evolution, including the structure of the interstellar medium, the formation of galactic winds, and the non-thermal pressure support of…

Astrophysics of Galaxies · Physics 2019-11-19 Yohan Dubois , Benoît Commerçon , Alexandre Marcowith , Loann Brahimi

Cosmic rays (CRs) with energies $\ll$ TeV comprise a significant component of the interstellar medium (ISM). Major uncertainties in CR behavior on observable scales (much larger than CR gyroradii) stem from how magnetic fluctuations scatter…

High Energy Astrophysical Phenomena · Physics 2024-01-24 Iryna S. Butsky , Philip F. Hopkins , Philipp Kempski , Sam B. Ponnada , Eliot Quataert , Jonathan Squire

We use a simple model for cosmic ray (CR) production and transport to assess the impact of CRs on $z$\,$=$\,$0$ galaxy, circumgalactic medium (CGM), and halo properties. To do so, we run the first suite of large-volume cosmological…

Astrophysics of Galaxies · Physics 2025-07-02 Rahul Ramesh , Dylan Nelson , Philipp Girichidis

The local cosmic-ray (CR) spectra are calculated for typical characteristic regions of a cold dense molecular cloud, to investigate two so far neglected mechanisms of dust charging: collection of suprathermal CR electrons and protons by…

Astrophysics of Galaxies · Physics 2015-11-05 Alexei Ivlev , Marco Padovani , Daniele Galli , Paola Caselli

Cosmic rays (CRs) are thought to play an important role in galaxy evolution. We study their effect when coupled to other important sources of feedback, namely supernovae and stellar radiation, by including CR anisotropic diffusion and…

Astrophysics of Galaxies · Physics 2022-05-27 Marion Farcy , Joakim Rosdahl , Yohan Dubois , Jérémy Blaizot , Sergio Martin-Alvarez

We study the effects of cosmic rays (CRs) on outflows from star-forming galaxies in the circum and inter-galactic medium (CGM/IGM), in high-resolution, fully-cosmological FIRE-2 simulations (accounting for mechanical and radiative stellar…

Cosmic ray (CR) hydrodynamics is a (re-)emerging field of high interest due to the importance of CRs for the dynamical evolution of the interstellar, the circumgalactic, and the intracluster medium. In these environments, CRs with GeV…

High Energy Astrophysical Phenomena · Physics 2021-11-03 Timon Thomas , Christoph Pfrommer

More and more observations have indicated the existence of slow diffusion phenomena in astrophysical environments, such as around the supernova remnants and pulsar $\gamma$-ray halos, where the diffusion coefficient of cosmic rays (CRs)…

High Energy Astrophysical Phenomena · Physics 2025-06-24 Yawen Xiao , Jianfu Zhang , Siyao Xu