Infrared images of ionized and molecular hydrogen emission in S106

We present high-resolution emission-line images of the central arcminute of S106 in Bry and H₂ ν = 1-0 S(1). The images were taken at UKIRT through a Fabry-Perot filter of 130 km s^-1 resolution using the infrared array camera IRCAM with a pixel size of 0″.62. The Bry emission shows a clear bipolar distribution which resembles that of the radio continuum emission. The central dark lane caused by the disk is wider in the Bry image than in comparable radio continuum images. The molecular hydrogen emission is predicted to originate in the dynamically shocked regions and/or in the photodissociation regions formed at the interface between the H II region and the clumpy molecular gas. For the case of S106, the peaks of the H₂ emission are located ∼5″ outside the corresponding Bry peaks; that is, further from the central star. The assumption that this displacement corresponds to the typical depth of the H₂ emitting zone in the photodissociation region, at which A_ν ≃ 2 mag, leads to a density estimate of ∼10⁵ cm^-3. This high density, together with the low excitation temperature reported earlier for S106, suggests that the origin of the thermal component in the H₂ emission measured by Tanaka et al. is either high-density fluorescence, that is, collisional de-excitation of the UV pumped H₂ in photodissociation regions formed on the dense molecular clumps beyond the ionization fronts, or it is radiation from slow shocks driven by the wind from the central source, propagating into the dense clumps. In either case, a novel physical environment is required to understand the observations.