We study the dense gas towards the young (~1 000yr) supernova remnant, RX J1713.7-3946, and the old (~10 000yr) supernova remnant, W28, using the Mopra radio telescope. Both of these remnants are TeV gamma-ray sources, which suggests local high energy particle populations. It follows that these objects are perfect targets for the study of the origin of cosmic-rays.
Gas density inhomogeneities may inhibit the passage of cosmic ray protons and/or provide extra cosmic ray proton target material. These two effects may be energy-dependent, hence may have signatures in gamma-ray observations (spatially and in energy spectra), therefore dense gas studies offer a novel way to test for the hadronic (p-p interactions) scenario and investigate the potential acceleration of cosmic rays in these objects.
We present the latest results from our Mopra 7 and 12mm surveys towards RX J1713.7-3946 and W28.