Resolving the hadronic accelerator IC 443 with Fermi-LAT and VERITAS

Supernova remnants (SNRs) close to molecular clouds are ideal astrophysical laboratories to study cosmic ray acceleration and injection into the Galaxy. The Galactic SNR IC 443 is among the brightest and best-studied of such systems, detected as an extended gamma-ray source at both GeV and TeV energies. Previous observations with the AGILE and Fermi-LAT gamma-ray space telescopes have shown a low-energy cutoff at <200 MeV indicating relativistic protons are responsible for gamma-ray emission. Observations by the MAGIC and VERITAS ground-based gamma-ray telescopes show a steepening spectrum at TeV energies. Now, with updated Fermi-LAT observations using 7 yr of Pass 8 data above 1 GeV, the gamma-ray morphology of IC 443 is revealed as an inhomogeneous shell. Multi-wavelength observations have mapped the detailed physical conditions across the interaction site between the SNR and cloud, allowing us to separately study gamma-ray emission regions on scales less than 10 pc. We find an excellent correlation between GeV gamma-rays and the TeV morphology determined by VERITAS. The combination of new VERITAS and Fermi-LAT observations of IC 443 allows an unprecedented study of the environmental dependence of cosmic-ray diffusion in and around a hadronic accelerator.