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Cosmic rays and high energy emission from starburst galaxies

Published online by Cambridge University Press:  17 August 2012

Brian C. Lacki  and
Todd A. Thompson
Brian C. Lacki
Affiliation:
Jansky Fellow & Institute for Advanced Study; Einstein Drive, Princeton, NJ 08540, USA email: brianlacki@ias.edu
Todd A. Thompson
Affiliation:
Department of Astronomy and Center for Cosmology and AstroParticle Physics, Ohio State University; 140 W. 18th Ave, Columbus, OH 43210, USA
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Abstract

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The nearby starburst galaxies M82 and NGC 253 are now detected in GeV and TeV γ-rays, allowing us to directly study cosmic rays (CRs) in starburst galaxies. Combined with radio observations, the detections constrain the propagation and density of CRs in these starbursts. We discuss the implications for “proton calorimetry”, whether CR protons cool through pion losses before escaping these galaxies. The ratio of γ-ray and radio luminosities constrains how much of the CR electron cooling is due to synchrotron losses. As for leptonic emission, we predict that synchrotron and Inverse Compton emission make up ~1–10% of the unresolved hard X-ray emission from M82, and a few percent or less of the total X-ray emission from starbursts. A detection of these components would inform us of the magnetic field strength and 10 – 100 TeV electron spectrum. We conclude by discussing the prospects for detecting leptonic MeV γ-rays from starbursts and the cosmic γ-ray background.

Keywords

galaxies: starburstgamma rays: theorygamma rays: observationsX-rays: galaxies
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 7 , Symposium S284: The Spectral Energy Distribution of Galaxies , September 2011 , pp. 393 - 396
Copyright
Copyright © International Astronomical Union 2012

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