Łukasz Tychoniec, Logan Francis, M. G. Navarro, Jakobus M. Vorster, Ewine F. van Dishoeck, Alessio Caratti o Garatti, Korash Assani, Valentin J. M. Le Gouellec, Benoît Tabone, Pamela Klaassen, Adriaan G. M. Janssen, K. Justtanont, Daniel Harsono, Pooneh Nazari, Simon Reyes, K. Slavicinska, C. Gieser, Tyler L. Bourke, Yao-Lun Yang, Brunella Nisini, Teresa Giannini, Henrik Beuther, R. Devaraj, Thomas P. Ray, Nashanty G. C. Brunken, Yuan Chen, M. L. van Gelder
Context. Protostellar winds can theoretically lift solids from the planet-forming disks, but direct evidence for launched dust has been scarce so far. Numerous atomic lines that are unique to mid-infrared (IR) wavelengths reveal refractories eroded from dust grains and provide information on wind properties in the earliest stages of the star formation process. Aims. We characterize the gas-phase composition, shock properties, and dust content of the jet from the Class 0 protostar BHR71-IRS1, one of the best cases of a resolved central jet inside a wide-angle wind. Methods. We present JWST MIRI-MRS spectral imaging of the inner 2000 au of the BHR71-IRS1 blueshifted side of the outflow. Atomic line intensities were compared to shock models to constrain the physical conditions and elemental abundances of the outflowing gas. Dust continuum maps were constructed from point spread function-subtracted cubes, and the spectral energy distribution of the dust was analyzed. Results. The ionized central jet of BHR71-IRS1 is spatially resolved and imaged for the first time, revealing a unique inventory of refractory, volatile, and noble-gas fine-structure lines (Fe, Ni, Co, Cl, S, Ne, and Ar). The emission is concentrated along four bright knots that wiggle along the jet axis. Point spread function-subtracted continuum maps reveal extended mid-IR continuum emission cospatial with the jet bullets and within the H 2 -traced outflow cone. Spectral energy distributions along the jet were fit together with the extinction, revealing a warm (200-400 K) and a cold (70-90 K) dust component. The shock modeling constrained by the mid-IR lines indicates a decline in the shock velocity from 70 to 35 km s −1 and in the pre-shock density from >10 5 to 4 × 10 4 cm −3 with distance from the protostar. Gas-phase Fe and Ni are measurably depleted relative to solar abundances. This is consistent with a substantial fraction of refractories remaining locked in grains in spite of the shocks. Conclusions. These JWST observations provide direct evidence that dust is launched in a Class 0 jet and at least partly survives shock processing. The richness of refractory tracers in the BHR71-IRS1 jet provides a window into the inner-disk composition at the onset of planet formation.