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PDRs4All II: JWST's NIR and MIR imaging view of the Orion Nebula Published: 8/31/2023 4:50:23 PM Updated: 8/31/2023 4:50:23 PM

Paper abstract: The JWST has captured the most detailed and sharpest infrared images evertaken of the inner region of the Orion Nebula, the nearest massive starformation region, and a prototypical highly irradiated dense photo-dissociationregion (PDR). We investigate the fundamental interaction of far-ultravioletphotons with molecular clouds. The transitions across the ionization front(IF), dissociation front (DF), and the molecular cloud are studied athigh-angular resolution. These transitions are relevant to understanding theeffects of radiative feedback from massive stars and the dominant physical andchemical processes that lead to the IR emission that JWST will detect in manyGalactic and extragalactic environments. Due to the proximity of the OrionNebula and the unprecedented angular resolution of JWST, these data reveal thatthe molecular cloud borders are hyper structured at small angular scales of0.1-1" (0.0002-0.002 pc or 40-400 au at 414 pc). A diverse set of features areobserved such as ridges, waves, globules and photoevaporated protoplanetarydisks. At the PDR atomic to molecular transition, several bright features aredetected that are associated with the highly irradiated surroundings of thedense molecular condensations and embedded young star. Toward the Orion BarPDR, a highly sculpted interface is detected with sharp edges and densityincreases near the IF and DF. This was predicted by previous modeling studies,but the fronts were unresolved in most tracers. A complex, structured, andfolded DF surface was traced by the H2 lines. This dataset was used to revisitthe commonly adopted 2D PDR structure of the Orion Bar. JWST provides us with acomplete view of the PDR, all the way from the PDR edge to the substructureddense region, and this allowed us to determine, in detail, where the emissionof the atomic and molecular lines, aromatic bands, and dust originate.