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Radio continuum observations of external galaxies provide us with an excellent outside view on the distribution of cosmic-ray electrons in the disc and halo. In this review, we summarise the current state of what we have learned from…

Astrophysics of Galaxies · Physics 2021-12-16 Volker Heesen

Given the multiple energy loss mechanisms of cosmic ray electrons in galaxies, the tightness of the infrared - radio continuum correlation is surprising. We extended the analytical model of galactic disks of Vollmer et al. (2017) by…

Astrophysics of Galaxies · Physics 2022-11-02 B. Vollmer , M. Soida , J. Dallant

An extinction-free estimator of the star-formation rate (SFR) of galaxies is critical for understanding the high-redshift universe. To this end, the nearly linear, tight correlation of far-infrared (FIR) and radio luminosity of star-forming…

Astrophysics of Galaxies · Physics 2021-09-22 Maria Werhahn , Christoph Pfrommer , Philipp Girichidis

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

Cosmic ray (CR) electrons are key tracers of non-thermal processes in galaxies, yet their spectra are often modelled under the untested assumption of steady state between injection and cooling. In this work, we present a time-dependent…

In star-forming galaxies, the far-infrared (FIR) and radio-continuum luminosities obey a tight empirical relation over a large range of star-formation rates (SFR). We examine magneto-hydrodynamic galaxy simulations with cosmic rays (CRs),…

Astrophysics of Galaxies · Physics 2022-07-20 Christoph Pfrommer , Maria Werhahn , Rüdiger Pakmor , Philipp Girichidis , Christine M. Simpson

A key for understanding the evolution of galaxies and in particular their star formation history will be future ultra-deep radio surveys. While star formation rates (SFRs) are regularly estimated with phenomenological formulas based on the…

Astrophysics of Galaxies · Physics 2017-04-12 Jennifer Schober , Dominik R. G. Schleicher , Ralf S. Klessen

The formation of galaxies is significantly influenced by galactic winds, possibly driven by cosmic rays due to their long cooling times and better coupling to plasma compared to radiation. In this study, we compare the radio observations of…

Astrophysics of Galaxies · Physics 2024-10-04 H. -H. Sandy Chiu , Mateusz Ruszkowski , Timon Thomas , Maria Werhahn , Christoph Pfrommer

Recent observations with the MeerKAT radio telescope reveal a unique population of faint non-thermal filaments pervading the central molecular zone (CMZ). Some of those filaments are organized into groups of almost parallel filaments,…

High Energy Astrophysical Phenomena · Physics 2020-02-26 Timon Thomas , Christoph Pfrommer , Torsten A. Enßlin

Current-day cosmic ray (CR) propagation studies use static Milky-Way models and fit parametrized source distributions to data. Instead, we use three-dimensional magneto-hydrodynamical (MHD) simulations of isolated galaxies with the…

High Energy Astrophysical Phenomena · Physics 2021-05-25 Maria Werhahn , Christoph Pfrommer , Philipp Girichidis , Ewald Puchwein , Rüdiger Pakmor

The physics of Cosmic ray (CR) transport remains a key uncertainty in assessing whether CRs can produce galaxy-scale outflows consistent with observations. In this paper, we elucidate the physics of CR-driven galactic winds for CR transport…

Astrophysics of Galaxies · Physics 2021-11-24 Eliot Quataert , Todd A. Thompson , Yan-Fei Jiang

The radio continuum spectra of 14 star-forming galaxies are investigated by fitting nonthermal (synchrotron) and thermal (free-free) radiation laws. The underlying radio continuum measurements cover a frequency range of ~325 MHz to 24.5 GHz…

Astrophysics of Galaxies · Physics 2018-03-28 Uli Klein , Ute Lisenfeld , Simon Verley

We model the transport and spectral evolution of 1-100 GeV cosmic ray (CR) electrons (CREs) in TIGRESS MHD simulations of the magnetized, multiphase interstellar medium. We post-process a kpc-sized galactic disk patch representative of the…

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

The thermal plasma of galaxy clusters lost most of its information on how structure formation proceeded as a result of dissipative processes. In contrast, non-equilibrium distributions of cosmic rays (CR) preserve the information about…

Astrophysics · Physics 2009-11-13 Christoph Pfrommer , Torsten A. Ensslin , Volker Springel

Context. Indirect observations of the cosmic-ray electron (CRE) distribution via synchrotron emission is crucial for deepening the understanding of the CRE transport in the interstellar medium, and in investigating the role of galactic…

High Energy Astrophysical Phenomena · Physics 2023-01-24 Julien Dörner , Patick Reichherzer , Julia Becker Tjus , Volker Heesen

Galactic winds play a key role in regulating the evolution of galaxies over cosmic time. In recent years, the role of cosmic rays (CR) in the formation of the galactic wind has increasingly gained attention. Therefore, we use radio…

Context. In order to understand galaxy evolution, it is essential to measure star formation rates (SFRs) across Cosmic times. Aims. The use of radio continuum emission as an extinction-free star formation tracer necessitates a good…

Astrophysics of Galaxies · Physics 2023-09-13 V. Heesen , S. Schulz , M. Brüggen , H. Edler , M. Stein , R. Paladino , A. Boselli , A. Ignesti , M. Fossati , R. -J. Dettmar

We construct one-zone steady-state models of cosmic ray (CR) injection, cooling, and escape over the entire dynamic range of the FIR-radio correlation (FRC), from normal galaxies to starbursts, over the redshift interval 0 <= z <= 10.…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-20 Brian C. Lacki , Todd A. Thompson

Observations of giant radio halos provide unambiguous evidence for the existence of cosmic ray (CR) electrons and magnetic fields in galaxy clusters. The physical mechanism generating radio halos is still heavily debated. We critically…

High Energy Astrophysical Phenomena · Physics 2011-09-28 Christoph Pfrommer , Torsten Ensslin , Francesco Miniati , Kandaswamy Subramanian

In the present paper we construct maps of polarized synchrotron radio emission of a whole galaxy, based on local models of the cosmic ray (CR) driven dynamo. We perform numerical simulations of the dynamo in local Cartesian domains, with…

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