2014ApJ...786..159R

We present the first high resolution UV spectra toward Herschel 36, a Trapezium-like system of high-mass stars contained within the Lagoon Nebula (M8, NGC 6523). The spectra reveal extreme rovibrational excitation of molecular hydrogen in material at a single velocity or very small range of velocities, with this component presumably lying near the star system and undergoing fluorescent excitation. The overall H₂ excitation is similar to, but apparently larger than, that seen toward HD 37903 which previously showed the largest vibrationally excited H₂column densities seen in UV absorption spectra. While the velocities of the highly excited H₂lines are consistent within each observation, it appears that they underwent a ∼60 km/s redshift during the 3.6 yr between observations. In neither case does the velocity of the highly excited material match the velocity of the bulk of the line-of-sight material which appears to mostly be in the foreground of M8. Recent work shows unusually excited CH and CH⁺ lines and several unusually broad diffuse interstellar bands toward Herschel 36. Along with the H₂excitation, all of these findings appear to be related to the extreme environment within ∼0.1 pc of the massive young stellar system.