HH 80/81: Structure and Kinematics of the Fastest Protostellar Outflow

Hubble Space Telescope (HST) images obtained in 2018 are combined with archival HST data taken in 1995 to detect changes and measure proper motions in the HH 80/81 shock complex, which is powered by the fastest known jet driven by a forming star, the massive object IRAS 18162-2048. Some persistent features close to the radio jet axis have proper motions of >1000 km s(-1) away from IRAS 18162-2048. About 3-5 pc downstream from the IRAS source and beyond HH 80/81, H alpha emission traces the rim of a parsec-scale bubble blown by the jet. Lower speed motions are seen in [S ii] away from the jet axis; these features have a large component of motion at right angles to the jet. We identify new HH objects and H-2 shocks in the counterflow opposite HH 80/81. The northeastern counterflow to HH 80/81 exhibits an extended but faint complex of 2.12 mu m H-2 shocks. The inner portion of the outflow is traced by dim 1.64 mu m [Fe ii] emission. The full extent of this outflow is at least 1500'' (similar to 10 pc in projection at a distance of 1.4 kpc). We speculate about the conditions responsible for the production of the ultrafast jet and the absence of prominent large-scale molecular outflow lobes.