Speaker
Description
The identification of the sources contributing to the acceleration of Galactic Cosmic Rays (CRs) is a long-standing puzzle. Assuming that CRs originate in the supernovae and winds of massive stars, starburst galaxies should provide an ideal environment for the production of gamma rays via the interaction of CRs with dense gas. Very-high-energy (VHE; E>100 GeV) gamma-ray emission was discovered from the starburst galaxy M82 using VERITAS in 2008-09. A more extensive campaign from 2008 to 2022, including these initial observations, yields a total of 254 hours of good-quality VERITAS data. Leveraging modern analysis techniques and the increased statistics, these VERITAS data show a significantly stronger VHE signal (~6.5 standard deviations), a better constrained spectrum (photon index ~ 2.3), and an improved flux measurement (~0.4% Crab Nebula flux) compared to the original result. The improved VERITAS measurements, when combined with various multi-wavelength data, enable modeling of the underlying emission. A purely leptonic scenario is found to be unlikely, and a hadronic scenario provides a good match to the spectral energy distribution. In this presentation, the results from VERITAS observations of M82 and the corresponding modeling will be shown.
