Speaker
Description
The origin of cosmic rays has been an active area of research since their discovery over a century ago. Supernova remnants (SNRs) are believed to be able to accelerate cosmic rays up to the ‘knee’ of the observed cosmic-ray spectrum via diffusive shock acceleration, a feature likely indicating the maximum cosmic-ray energy achieved in our Galaxy. Although the acceleration at SNR shocks has been extensively modelled, it is still not observationally clear that cosmic rays are able to escape these sources. After acceleration, cosmic rays may escape the shock front and diffuse into the surrounding environment where they could interact with ambient gas to produce gamma rays. Detection of gamma-ray emission outside the observed shell of an SNR will provide evidence for cosmic-ray escape from SNRs. We outline here an approach to search for escaped cosmic rays from SNRs using Fermi-LAT data. In an attempt to account for the PSF effects, we have applied the Pylira package to the Fermi-LAT count maps of W28. We also outline a radial profile method that may potentially be used to search for cosmic-ray escape from SNRs.
