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We study the ionization and excitation structure of the interstellar mediumin the late-stage gas-rich galaxy merger NGC 6240 using a suite of emissionline maps at $\sim$25 pc resolution from the Hubble Space Telescope, Keck NIRC2with Adaptive Optics, and ALMA. NGC 6240 hosts a superwind driven by intensestar formation and/or one or both of two active nuclei; the outflows producebubbles and filaments seen in shock tracers from warm molecular gas (H$_2$2.12$\mu$m) to optical ionized gas ([O III], [N II], [S II], [O I]) and hotplasma (Fe XXV). In the most distinct bubble, we see a clear shock front tracedby high [O III]/H$\beta$ and [O III]/[O I]. Cool molecular gas (CO(2-1)) isonly present near the base of the bubble, towards the nuclei launching theoutflow. We interpret the lack of molecular gas outside the bubble to mean thatthe shock front is not responsible for dissociating molecular gas, and concludethat the molecular clouds are partly shielded and either entrained briefly inthe outflow, or left undisturbed while the hot wind flows around them.Elsewhere in the galaxy, shock-excited H$_2$ extends at least $\sim$4 kpc fromthe nuclei, tracing molecular gas even warmer than that between the nuclei,where the two galaxies' interstellar media are colliding. A ridgeline of high[O III]/H$\beta$ emission along the eastern arm aligns with the south nucleus'stellar disk minor axis; optical integral field spectroscopy from WiFeSsuggests this highly ionized gas is centered at systemic velocity and likelyphotoionized by direct line-of-sight to the south AGN.

Tracing the Ionization Structure of the Shocked Filaments of NGC 6240