Excitation conditions and energetics of the dense gas in M17 SW

Abstract

The chemical and energetic conditions created by radiative feedback are probed with observations of multiple molecular transitions toward M17 SW. Extensive maps, including the 12 CO J = 16 → 15, J = 12 → 11, and J = 11 → 10 lines, as well as the HCN J = 8 → 7 and HCO + J = 9 → 8 transitions, were obtained with the dual band receiver GREAT on board the SOFIA airborne telescope, and with the ground based APEX and IRAM 30 m telescopes. These data provide extensive line spectral energy distributions (LSEDs) of the CO, HCN and HCO + molecules (and their isotopologues). The excitation conditions of the three species are estimated simultaneously using the same density and temperature in a two-phase non-LTE radiative transfer model of the LSEDs.