Nonthermal Emission from Star-Forming Galaxies

TL;DR

This paper reviews high-energy gamma-ray emissions from star-forming galaxies, exploring how supernova-driven particles produce nonthermal radiation, and assesses their energy densities across different galactic environments.

Contribution

It provides a comprehensive review of nonthermal processes in star-forming galaxies and quantifies particle energy densities related to supernova activity.

Findings

Gamma-ray emissions observed in starburst galaxies M82 and NGC253.

Particle energy densities vary from 0.1 eV/cm^3 to 100 eV/cm^3 depending on star formation activity.

The relation between supernova activity and nonthermal radiation is characterized.

Abstract

The detections of high-energy gamma-ray emission from the nearby starburst galaxies M82 & NGC253, and other local group galaxies, broaden our knowledge of star-driven nonthermal processes and phenomena in non-AGN star-forming galaxies. We review basic aspects of the related processes and their modeling in starburst galaxies. Since these processes involve both energetic electrons and protons accelerated by SN shocks, their respective radiative yields can be used to explore the SN-particle-radiation connection. Specifically, the relation between SN activity, energetic particles, and their radiative yields, is assessed through respective measures of the particle energy density in several star-forming galaxies. The deduced energy densities range from O(0.1) eV/cm^3 in very quiet environments to O(100) eV/cm^3 in regions with very high star-formation rates.