2020ApJ...902L...1H

We present the first wide-field near-infrared adaptive-optics images of Carina's Western Wall (G287.38-0.62), one of the brightest and most well-defined irradiated interfaces known in a region of massive star formation. The new narrowband H₂ 2.12 µm, Br-γ and K-continuum images from Gemini South trace the photoevaporative flow from the cloud and identify locations where UV radiation from the surrounding massive stars excites molecular hydrogen to fluoresce. With a field of view of ∼1.'5 x 2.'9 and spatial resolution between 60 and 110 mas, the new images show a spectacular level of detail over a large area, and presage what the James Webb Space Telescope (JWST) should achieve. The Wall is convex in shape, with a large triangular-shaped extension near its apex. The interface near the apex consists of 3-4 regularly spaced ridges with projected spacings of ∼2000 au, suggestive of a large-scale dynamically important magnetic field. The northern edge of the Wall breaks into several swept-back fragments of width ∼1800 au that resemble Kelvin-Helmholtz instabilities, and the southern part of the Wall also shows complex morphologies including a sinusoidal-like variation with a half-wavelength of 2500 au. Though the dissociation front must increase the density along the surface of the Wall, it does not resolve into pillars that point back to the ionization sources, as could occur if the front triggered new stars to form. We discovered that MHO 1630, an H₂ outflow with no clear driving source in the northern portion of the Wall, consists of a series of bow shocks arrayed in a line.