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Arxiv: JWST Observations of Young protoStars (JOYS). HH 211: the textbook case of a protostellar jet and outflow Published: 9/24/2024 4:02:58 PM Updated: 9/24/2024 4:02:58 PM

Paper abstract: We use the James Webb Space Telescope (JWST) and its Mid-Infrared Instrument(MIRI) (5-28 um), to study the embedded HH 211 flow. We map a 0.95'x0.22'region, covering the full extent of the blue-shifted lobe, the centralprotostellar region, and a small portion of the red-shifted lobe. The jetdriving source is not detected even at the longest mid-IR wavelengths. Theoverall morphology of the flow consists of a highly collimated jet, mostlymolecular (H2, HD) with an inner atomic ([FeI], [FeII], [SI], [NiII])structure. The jet shocks the ambient medium, producing several largebow-shocks, rich in forbidden atomic and molecular lines, and is driving an H2molecular outflow, mostly traced by low-J, v=0 transitions. Moreover, 0-0 S(1)uncollimated emission is also detected down to 2"-3" (~650-1000 au) from thesource, tracing a cold (T=200-400 K), less dense and poorly collimatedmolecular wind. The atomic jet ([FeII] at 26 um) is detected down to ~130 aufrom source, whereas the lack of H2 emission close to the source is likely dueto the large visual extinction. Dust continuum-emission is detected at theterminal bow-shocks, and in the blue- and red-shifted jet, being likely dustlifted from the disk. The jet shows an onion-like structure, with layers ofdifferent size, velocity, temperature, and chemical composition. Moreover,moving from the inner jet to the outer bow-shocks, different physical,kinematic and excitation conditions for both molecular and atomic gas areobserved. The jet mass-flux rate, momentum, and momentum flux of the warm H2component are up to one order of magnitude higher than those inferred from theatomic jet component. Our findings indicate that the warm H2 component is theprimary mover of the outflow, namely it is the most significant dynamicalcomponent of the jet, in contrast to jets from more evolved YSOs, where theatomic component is dominant.