Gamma-rays from pulsar wind nebulae in starburst galaxies

TL;DR

This paper demonstrates that pulsar wind nebulae significantly contribute to the TeV gamma-ray emission observed in starburst galaxies, challenging the previous assumption that cosmic ray interactions are the primary source.

Contribution

It introduces the idea that pulsar wind nebulae, rather than just cosmic ray interactions, are major sources of gamma rays in starburst galaxies.

Findings

A single pulsar wind nebula emits about ten times the Sun's luminosity above 1 TeV.

Approximately 30,000 pulsar wind nebulae in a galaxy can explain observed gamma-ray levels.

Pulsar wind nebulae are a major contributor to gamma-ray luminosity in starburst galaxies.

Abstract

Recently, gamma-ray emission at TeV energies has been detected from the starburst galaxies NGC253 (Acero et al., 2009) and M82 (Acciari et al., 2009. It has been claimed that pion production due to cosmic rays accelerated in supernova remnants interacting with the interstellar gas is responsible for the observed gamma rays. Here, we show that the gamma-ray pulsar wind nebulae left behind by the supernovae contribute to the TeV luminosity in a major way. A single pulsar wind nebula produces about ten times the total luminosity of the Sun at energies above 1 TeV during a lifetime of 10^5 years. A large number of 3x10^4 pulsar wind nebulae expected in a typical starburst galaxy at a distance of 4 Mpc can readily produce the observed TeV gamma rays.