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Starburst galaxies are efficient $\gamma$-ray producers, because their high supernova rates generate copious cosmic ray (CR) protons, and their high gas densities act as thick targets off which these protons can produce neutral pions and…

High Energy Astrophysical Phenomena · Physics 2020-02-26 Mark R. Krumholz , Roland M. Crocker , Siyao Xu , A. Lazarian , M. T. Rosevear , Jasper Bedwell-Wilson

The microphysics of ~GeV cosmic ray (CR) transport on galactic scales remain deeply uncertain, with almost all studies adopting simple prescriptions (e.g. constant-diffusivity). We explore different physically-motivated, anisotropic,…

High Energy Astrophysical Phenomena · Physics 2022-03-18 Philip F. Hopkins , Jonathan Squire , T. K. Chan , Eliot Quataert , Suoqing Ji , Dusan Keres , Claude-Andre Faucher-Giguere

Cosmic rays (CRs) with ~GeV energies can contribute significantly to the energy and pressure budget in the interstellar, circumgalactic, and intergalactic medium (ISM, CGM, IGM). Recent cosmological simulations have begun to explore these…

Cosmic ray propagation in the Milky Way and other galaxies is largely diffusive, with mean free path determined primarily by pitch angle scattering from hydromagnetic waves with wavelength of order the cosmic ray gyroradius. In the theory…

High Energy Astrophysical Phenomena · Physics 2020-02-19 Ellen G. Zweibel

In this second paper in a series dedicated to characterizing shear layers via 2D hybrid (kinetic ions -- fluid electrons) simulations, we study the dynamical role of nonthermal particles (cosmic rays, CRs), either spontaneously generated or…

High Energy Astrophysical Phenomena · Physics 2026-04-15 Naixin Liang , Damiano Caprioli

The circumgalactic medium (CGM) plays a critical role in galaxy evolution, influencing gas flows, feedback processes, and galactic dynamics. Observations show a substantial cold gas reservoir in the CGM, but the mechanisms driving its…

Astrophysics of Galaxies · Physics 2025-06-11 Matthias Weber , Timon Thomas , Christoph Pfrommer , Ruediger Pakmor

The nature of cosmic rays (CRs) and cosmic ray transport in galaxy clusters is probed by a number of observations. Radio observations reveal the synchrotron radiation of cosmic ray electrons (CRe) spiraling around cluster magnetic fields.…

High Energy Astrophysical Phenomena · Physics 2019-06-26 Joshua Wiener , Ellen G. Zweibel

We investigate the interplay of cosmic ray (CR) propagation and advection in galaxy clusters. Propagation in form of CR diffusion and streaming tends to drive the CR radial profiles towards being flat, with equal CR number density…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-19 Torsten A. Ensslin , Christoph Pfrommer , Francesco Miniati , Kandaswamy Subramanian

We study winds in high redshift galaxies driven by a relativistic cosmic ray (proton) component in addition to the hot thermal gas component. Cosmic rays (CRs) are likely to be efficiently generated in supernova shocks inside galaxies. We…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-14 Saumyadip Samui , Kandaswamy Subramanian , Raghunathan Srianand

Cosmic rays are transported out of the galaxy by diffusion and advection due to streaming along magnetic field lines and resonant scattering off self-excited MHD waves. Thus momentum is transferred to the plasma via the frozen-in waves as a…

High Energy Astrophysical Phenomena · Physics 2013-04-05 E. A. Dorfi , D. Breitschwerdt

Galactic winds regulate star formation in disk galaxies and help to enrich the circum-galactic medium. They are therefore crucial for galaxy formation, but their driving mechanism is still poorly understood. Recent studies have demonstrated…

Astrophysics of Galaxies · Physics 2018-01-31 Svenja Jacob , Rüdiger Pakmor , Christine M. Simpson , Volker Springel , Christoph Pfrommer

There is an observational correlation between astrophysical shocks and non-thermal particle distributions extending to high energies. As a first step toward investigating the possible feedback of these particles on the shock at the…

High Energy Astrophysical Phenomena · Physics 2012-01-31 Thomas Stroman , Martin Pohl , Jacek Niemiec , Antoine Bret

We study the properties of cosmological shock waves identified in high-resolution, N-body/hydrodynamic simulations of a $\Lambda$CDM universe and their role on thermalization of gas and acceleration of nonthermal, cosmic ray (CR) particles.…

Astrophysics · Physics 2008-11-26 Dongsu Ryu , Hyesung Kang , Eric Hallman , T. W. Jones

We revisit propagation of galactic cosmic rays (CRs) in light of recent advances in CR diffusion theory in realistic interstellar turbulence. We use a tested model of turbulence in which it has been shown that fast modes dominate scattering…

High Energy Astrophysical Phenomena · Physics 2015-06-17 Carmelo Evoli , Huirong Yan

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 rays (CRs) are the primary driver of ionization in star forming molecular clouds (MCs). Despite their potential impacts on gas dynamics and chemistry, no simulations of star cluster formation following the creation of individual…

Astrophysics of Galaxies · Physics 2024-07-26 Margot Fitz Axen , Stella Offner , Phillip F. Hopkins , Mark R. Krumholz , Michael Y. Grudic

When a magnetised, thermal plasma containing a shock wave efficiently accelerates Cosmic Rays (CR) a reaction is exerted on the fluid structure. The simplest description of this process involves three conservation equations for the…

Astrophysics · Physics 2007-05-23 P. Duffy , L. O'C. Drury , H. J. Voelk

The nonresonant streaming instability (Bell instability) plays a pivotal role in the acceleration and confinement of cosmic rays (CRs); yet, the exact mechanism responsible for its saturation and the magnitude of the final amplified…

High Energy Astrophysical Phenomena · Physics 2024-04-09 Georgios Zacharegkas , Damiano Caprioli , Colby Haggerty , Siddhartha Gupta , Benedikt Schroer

We investigate the transport of spectrally resolved cosmic ray (CR) protons with kinetic energies between $1-100$ GeV within the dynamic, multiphase interstellar medium (ISM), using a two-moment CR fluid solver applied to a TIGRESS MHD…

High Energy Astrophysical Phenomena · Physics 2025-07-02 Lucia Armillotta , Eve C. Ostriker , Nora B. Linzer

Numerical simulations shed light onto earlier not trackable problem of magnetohydrodynamic (MHD) turbulence. They allowed to test the predictions of different models and choose the correct ones. Inevitably, this progress calls for revisions…

Astrophysics · Physics 2007-12-27 Huirong Yan , A. Lazarian