Starburst Galactic Nuclei as Light Dark Matter Laboratories
Antonio Ambrosone, Marco Chianese, Damiano F. G. Fiorillo, A. Marinelli, Gennaro Miele
Abstract
Starburst galaxies are well-motivated astrophysical emitters of high-energy gamma rays. They are well-known cosmic-ray ``reservoirs,'' thanks to their expected large magnetic field turbulence which confine high-energy protons for $\ensuremath{\sim}{10}^{5}\text{ }\text{ }\mathrm{years}$. Over such long times, cosmic-ray transport can be significantly affected by scatterings with sub-GeV dark matter. Here we point out that this scattering distorts the cosmic-ray spectrum, and the distortion can be indirectly observed by measuring the gamma rays produced by cosmic rays via hadronic collisions. Present gamma-ray data show no sign of such a distortion, leading to stringent bounds on the cross section between protons and dark matter. These are highly complementary with current bounds and have large room for improvement with the future gamma-ray measurements in the 0.1--10 TeV range from the Cherenkov Telescope Array, which can strengthen the limits by as much as 2 orders of magnitude.