Evidence of a spectral break in the gamma-ray emission of the disk component of Large Magellanic Cloud: a hadronic origin?

Abstract

It has been suggested that high-energy gamma-ray emission ($>100\mathrm{MeV}$) of nearby star-forming galaxies may be produced predominantly by cosmic rays colliding with the interstellar medium through neutral pion decay. The pion-decay mechanism predicts a unique spectral signature in the gamma-ray spectrum, characterized by a fast rising spectrum and a spectral break below a few hundreds of MeV. We here report the evidence of a spectral break around 500 MeV in the disk emission of Large Magellanic Cloud (LMC), which is found in the analysis of the gamma-ray data extending down to 60 MeV observed by {\it Fermi}-Large Area Telescope. The break is well consistent with the pion-decay model for the gamma-ray emission, although leptonic models, such as the electron bremsstrahlung emission, cannot be ruled out completely.

11 pages, 4 figures, Accepted by ApJ

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Cited by in corpus (4)

• Discovery of GeV gamma-ray emission from the LMC B0443-6657 with the Fermi Large Area Telescope
• GeV emission of gamma-ray binary with pulsar scenario
• Gamma-ray emission toward supergiant shells in the Large Magellanic Cloud
• Diffuse non-thermal emission in the disks of the Magellanic Clouds