Connecting the ISM to TeV PWNe and PWN candidates

We investigate the interstellar medium towards seven TeV gamma-ray sources thought to be pulsar wind nebulae using Mopra molecular line observations at 7mm [ CS(1-0), SiO(1-0, v = 0)], Nanten CO(1-0) data and the Southern Galactic Plane Survey/ GASS HI survey. We have discovered several dense molecular clouds co-located to these TeV gamma-ray sources, which allows us to search for cosmic rays coming from progenitor SNRs or, potentially, from pulsar wind nebulae. We notably found SiO(1-0, v= 0) emission towards HESS J1809-193, highlighting possible interaction between the adjacent supernova remnant SNR G011.0-0.0 and the molecular cloud at d similar to 3.7 kpc. Using morphological features, and comparative studies of our column densities with those obtained from X-raymeasurements, we claim a distance d similar to 8.6 -9.7 kpc for SNRG292.2-00.5, d similar to 3.5-5.6 kpc for PSR J1418-6058 and d similar to 1.5 kpc for the new SNR candidate found towards HESS J1303-631. From ourmass and density estimates of selected molecular clouds, we discuss signatures of hadronic/ leptonic components from pulsar wind nebulae and their progenitor SNRs. Interestingly, the molecular gas, which overlaps HESS J1026-582 at d similar to 5 kpc, may support a hadronic origin. We find however that this scenario requires an undetected cosmic-ray accelerator to be located at d < 10 pc from the molecular cloud. For HESS J1809-193, the cosmic rays which have escaped SNR G011.0-0.0 could contribute to the TeV gamma-ray emission. Finally, from the hypothesis that at most 20% the pulsar spin down power could be converted into CRs, we find that among the studied pulsar wind nebulae, only those from PSR J1809-1917 could potentially contribute to the TeV emission.