James Webb Space Telescope Feed Post

New insights in the bubble wall of NGC 3324: intertwined sub-structures and a bipolar morphology uncovered by JWST

a) The panel shows the Spitzer-GLIMPSE 5.8 µm image of the bubble rim or cosmic cliffs NGC 3324 (see a dotted-dashed box in Figure A1a). The area of the image is ~2.'79 × 6.'74 (central coordinates: a2000 = 10h36m49.s02; d2000 = -58?37'25.''52). The positions of four clumps traced in the LABOCA 870 µm continuum map (Duronea et al. 2015) are marked by filled stars. Open circles and open diamonds show the locations of YSOs (from Kuhn et al. 2021) and molecular outflows (from Reiter et al. 2022), respectively. A dotted curve (in red) shows the footprint of the sharp edge. b) Spitzer-GLIMPSE ratio map of 4.5 µm/3.6 µm emission. c) The panel displays the JWST F335M image. In each panel, a small region “sm1” is highlighted by a solid box and a scale bar shows a size of 0.55 pc at a distance of 2.2 kpc. Abstract: We report the discovery of intertwined/entangled sub-structures towards the bubble wall of NGC 3324 below a physical scale of 4500 AU, which is the sharp edge/ionization front/elongated structure traced at the interface between the HII region and the molecular cloud. The sharp edge appears wavy in the Spitzer 3.6-8.0 µm images (resolution ~2''). Star formation signatures have mostly been traced on one side of the ionization front, which lies on the molecular cloud's boundary. The James Webb Space Telescope's (JWST) near- and mid-infrared images (resolution ~0.07''-0.7'') are employed to resolve the sharp edge, which has a curvature facing the exciting O-type stars. The elongated structures are associated with the 3.3 µm polycyclic aromatic hydrocarbon (PAH) emission, the 4.05 µm ionized emission, and the 4.693 µm H2 emission. However, the PAH-emitting structures are depicted between the other two. The H2 emission reveals numerous intertwined sub-structures which are not prominently traced in the 3.3 µm PAH emission. The separation between two sub-structures in the H2 emission is ~1.1'' or 2420 AU. The intertwined sub-structures are traced in the spatial areas associated with the neutral to H2 transition zone, suggesting the origin of these structures by ``thin-shell' instability. Furthermore, an arc-like feature traced in the Spitzer 3.6-8.0 µm images is investigated as a bipolar HII region (extent ~0.35 pc) at Td ~25-28~K using the JWST images. A massive star candidate VPHAS-OB1 #03518 seems to be responsible for the bipolar HII region.