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We probe the chemical and energetic conditions in dense gas created byradiative feedback through observations of multiple CO, HCN and HCO$^+$transitions toward the dense core of M17 SW. We used the dual band receiverGREAT on board the SOFIA airborne telescope to obtain maps of the $J=16-15$,$J=12-11$, and $J=11-10$ transitions of $^{12}$CO. We compare these maps withcorresponding APEX and IRAM 30m telescope data for low- and mid-$J$ CO, HCN andHCO$^+$ emission lines, including maps of the HCN $J=8-7$ and HCO$^+$ $J=9-8$transitions. The excitation conditions of $^{12}$CO, HCO$^+$ and HCN areestimated with a two-phase non-LTE radiative transfer model of the linespectral energy distributions (LSEDs) at four selected positions. The energybalance at these positions is also studied. We obtained extensive LSEDs for theCO, HCN and HCO$^+$ molecules toward M17 SW. The LSED shape, particularly thehigh-$J$ tail of the CO lines observed with SOFIA/GREAT, is distinctive for theunderlying excitation conditions. The critical magnetic field criterion impliesthat the cold cloudlets at two positions are partially controlled by processesthat create and dissipate internal motions. Supersonic but sub-Alfv\'enicvelocities in the cold component at most selected positions indicates thatinternal motions are likely MHD waves. Magnetic pressure dominates thermalpressure in both gas components at all selected positions, assuming randomorientation of the magnetic field. The magnetic pressure of a constant magneticfield throughout all the gas phases can support the total internal pressure ofthe cold components, but it cannot support the internal pressure of the warmcomponents. If the magnetic field scales as $B \propto n^{2/3}$, then theevolution of the cold cloudlets at two selected positions, and the warmcloudlets at all selected positions, will be determined by ambipolar diffusion.

Disentangling the excitation conditions of the dense gas in M17 SW