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arXiv · 1407.3391

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

Qing-Wen Tang·Xiang-Yu Wang·Pak-Hin Thomas Tam
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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 $\sim5.5σ$ 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.

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Qing-Wen Tang, Xiang-Yu Wang, Pak-Hin Thomas Tam. 2014-08-08. Discovery of GeV emission from the direction of the luminous infrared galaxy NGC 2146. https://doi.org/10.1088/0004-637x%2F794%2F1%2F26

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