Speaker
Ralph Bird
(UCD Dublin)
Description
Diffuse gamma rays are tracers of cosmic rays, providing information on their origin and diffusion. M 31 (the Andromeda Galaxy) is the closest spiral galaxy to the Milky Way (d = 750 kpc) and is very well studied at all wavelengths, thus it is a prime target for the study of diffuse gamma-ray emission. The very-high-energy (VHE, E > 100 GeV) gamma-ray observatory VERITAS has conducted 45 hours of observations of M 31 and an upper limit on the VHE flux will be presented. An updated Fermi-LAT (100 MeV < E < 300 GeV) analysis will also be presented. These observations will be compared with predictions of the gamma-ray flux derived from the inelastic scattering of VHE cosmic rays of the interstellar medium (ISM) and the interstellar radiation field. M 31 provides an ideal opportunity to probe these mechanisms. Its proximity and spatial extent, significantly larger than the VERITAS point spread function but smaller than the field-of-view, enables the star-forming ring, 10 kpc from the galaxy core, with its dense ISM and numerous supernova remnants to be resolved.
| Registration number following "ICRC2015-I/" | 884 |
|---|---|
| Collaboration | VERITAS |
Primary author
Ralph Bird
(UCD Dublin)
