SNR Kes 17 and ISM from radio and gamma rays

Towards the western boundary of Kes 17, no signatures of carbon monoxide emissions are detected above 3 sigma, despite previously reported infrared observations that revealed shocked molecular gas at this location. This suggests the existence of a CO-dark interacting molecular gas, a phenomenon also recorded in other Galactic SNRs (e.g. CTB 37A and RX J1713.7-3946) that reveals itself both in the infrared and gamma-ray domains.

Additionally, by analysing ~14.5yr of continuously collected data from the Large Area Telescope on board the satellite Fermi, we determined that the best-fit power-law photon index for the 0.3-300GeV gamma-ray emission from the Kes 17 region is Gamma=2.39+/-0.04^+0.063^_-0.114_(+/-stat+/-syst), in agreement with prior studies. The energy flux is (2.98+/-0.14)x10^-11^erg/cm^2^/s, implying a luminosity (2.22+/-0.45)x10^35^erg/s at ~8kpc.

Finally, we successfully modelled the multiwavelength spectral energy distribution by incorporating the radio-synchrotron spectrum and the new measurements of GeV gamma-rays. Our analysis indicates that the observed gamma-ray flux most likely originates from the interaction of Kes 17 with a western dark CO zone with a proton density n_p_~400cm^-3^.