Constraints on the Emission of Gamma-Rays from M31 with HAWC

Document Type

Article

Publication Date

4-10-2020

Department

Department of Physics; Department of Materials Science and Engineering

Abstract

Cosmic rays, along with stellar radiation and magnetic fields, are known to make up a significant fraction of the energy density of galaxies such as the Milky Way. When cosmic rays interact in the interstellar medium, they produce gamma-ray emission which provides an important indication of how the cosmic rays propagate. Gamma-rays from the Andromeda galaxy (M31), located 785 kpc away, provide a unique opportunity to study cosmic-ray acceleration and diffusion in a galaxy with a structure and evolution very similar to the Milky Way. Using 33 months of data from the High Altitude Water Cherenkov Observatory, we search for teraelectronvolt gamma-rays from the galactic plane of M31. We also investigate past and present evidence of galactic activity in M31 by searching for Fermi bubble-like structures above and below the galactic nucleus. No significant gamma-ray emission is observed, so we use the null result to compute upper limits on the energy density of cosmic rays >10 TeV in M31.

Publisher's Statement

© 2020. The American Astronomical Society. All rights reserved. Publisher’s version of record: https://doi.org/10.3847/1538-4357/ab7999

Publication Title

Astrophysical Journal

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