Discovery of GeV emission from the direction of the luminous infrared galaxy NGC 2146

Abstract

Recent detection of high-energy gamma-ray emission from starburst galaxies M82 and NGC 253 suggests that starburst galaxies are huge reservoirs of cosmic rays and these cosmic rays convert a significant fraction of their energy into gamma-rays by colliding with the dense interstellar medium. In this paper, we report the search for high-energy gamma-ray emission from several nearby star-forming and starburst galaxies using the 68 month data obtained with the Fermi Large Area Telescope. We found a $\sim 5.5\sigma$ detection of gamma-ray emission above 200{\rm MeV} from a source spatially coincident with the location of the luminous infrared galaxy NGC~2146. Taking into account also the temporal and spectral properties of the gamma-ray emission, we suggest that the gamma-ray source is likely to be the counterpart of NGC~2146. The gamma-ray luminosity suggests that cosmic rays in NGC~2146 convert most of their energy into secondary pions, so NGC~2146 is a "proton calorimeter". It is also found that NGC~2146 obeys the quasi-linear scaling relation between the gamma-ray luminosity and total infrared luminosity for star-forming galaxies, strengthening the connection between massive star formation and gamma-ray emission of star-forming galaxies. Possible TeV emission from NGC~2146 is predicted and the implications for high-energy neutrino emission from starburst galaxies are discussed.

Accepted by ApJ, discussions revised following the referee report, results and conclusions unchanged

References in corpus (6)

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• CGRaBS: An All-Sky Survey of Gamma-Ray Blazar Candidates
• A connection between star formation activity and cosmic rays in the starburst galaxy M 82
• Detection of Gamma Rays From a Starburst Galaxy
• The Starburst Contribution to the Extra-Galactic Gamma-Ray Background
• A far-IR view of the starburst driven superwind in NGC 2146

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