Cosmic-ray induced gamma-ray emission from the starburst galaxy NGC 253

Xilu Wang, Brian D. Fields

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Cosmic rays in galaxies interact with the interstellar medium and give us a direct view of nuclear and particle interactions in the cosmos. For example, cosmic-ray proton interactions with interstellar hydrogen produce gamma rays via pcrpism→ π0→γγ. For a "normal" star-forming galaxy like the Milky Way, most cosmic rays escape the Galaxy before such collisions, but in starburst galaxies with dense gas and huge star formation rate, most cosmic rays do suffer these interactions [1,2]. We construct a "thick-target" model for starburst galaxies, in which cosmic rays are accelerated by supernovae, and escape is neglected. This model gives an upper limit to the gamma-ray emission. Only two free parameters are involved in the model: cosmic-ray proton acceleration energy rate from supernova and the proton injection spectral index. The pionic gamma-radiation is calculated from 10 MeV to 10 TeV for the starburst galaxy NGC 253, and compared to Fermi and HESS data. Our model fits NGC 253 well, suggesting that cosmic rays in this starburst are in the thick target limit, and that this galaxy is a gamma-ray calorimeter.

Original languageEnglish (US)
Title of host publicationSeventh European Summer School on Experimental Nuclear Astrophysics - Proceedings of the 7th European Summer School on Experimental Nuclear Astrophysics
PublisherAmerican Institute of Physics Inc.
Pages231-233
Number of pages3
ISBN (Print)9780735412293
DOIs
StatePublished - Jan 1 2014
Event7th European Summer School on Experimental Nuclear Astrophysics - Sicily, Italy
Duration: Sep 15 2013Sep 27 2013

Publication series

NameAIP Conference Proceedings
Volume1595
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

Other7th European Summer School on Experimental Nuclear Astrophysics
CountryItaly
CitySicily
Period9/15/139/27/13

Keywords

  • NGC 253
  • cosmic-rays
  • gamma-rays
  • starburst galaxies

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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