Radiative Feedback: Multi-line Study of the Photo-Dissociation Region M17-SW

The radiation from massive stars, photo-dissociating and ionizing their parental molecular cloud, is a significant feedback process regulating star formation. To study it, we mapped the photo-dissociation region (PDR) M17-SW in several fine structure and high-J CO lines with FIFI-LS, the far-infrared integral spectrometer aboard SOFIA. An analysis of the CO and \oi146\um line intensities, combined with the far infrared intensity, allows us to create a density and UV intensity map using a one dimensional model. The density map reveals a sudden change in the gas density crossing the PDR. The strengths and limits of the model and the locations of the ionization and photo-dissociation fronts of the edge-on PDR are discussed.