James Webb Space Telescope Feed Post

JWST Observations of Starbursts: Polycyclic Aromatic Hydrocarbon Emission at the base of the M 82 Galactic Wind

Small scale structure in the PAH emission. The top panel shows the same image as Figure 5 with a grid superimposed. The bottom panel shows the result of removing a version of the image smoothed on 5'' (87 pc) scales, a technique known as unsharp masking, to bring up the structure below those scales. This highlights the network of fine filaments and the bright walls of bubble-like structures present in the PAH image. The panels to the right show 7'' × 7'' zooms into the top panel, highlighting the rich substructure in the outflow. Their gray scale is linear and adjusted separately for each panel, as indicated by the accompanying colorbar (in MJy/sr). Abstract: We present new observations of the central 1 kpc of the M 82 starburst obtained with the James Webb Space Telescope (JWST) near-infrared camera (NIRCam) instrument at a resolution ~0.05"-0.1" (~1-2 pc). The data comprises images in three mostly continuum filters (F140M, F250M, and F360M), and filters that contain [FeII] (F164N), H2 v=1-0 (F212N), and the 3.3 um PAH feature (F335M). We find prominent plumes of PAH emission extending outward from the central starburst region, together with a network of complex filamentary substructure and edge-brightened bubble-like features. The structure of the PAH emission closely resembles that of the ionized gas, as revealed in Paschen alpha and free-free radio emission. We discuss the origin of the structure, and suggest the PAHs are embedded in a combination of neutral, molecular, and photoionized gas.