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

TL;DR

This study combines HST images from 1995 and 2018 to analyze the structure and motion of the HH 80/81 protostellar outflow, revealing ultra-fast jets, new shock features, and complex kinematics over a 10 parsec scale.

Contribution

It provides the first detailed proper motion measurements of the HH 80/81 outflow, uncovering ultra-fast jet components and new shock features, enhancing understanding of massive star formation outflows.

Findings

Proper motions > 1000 km/s near the jet axis.

Detection of new HH objects and H2 shocks in the counterflow.

Full outflow extent of at least 10 parsecs.

Abstract

Hubble Space Telescope 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 grater than 1,000 km/s away from IRAS 18162-2048. About 3 to 5 parsecs 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 [Sii] 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 H2 shocks in the counterflow opposite HH 80/81. The northeastern counterflow to HH 80/81 exhibits an extended but faint complex of 2.12 um H2 shocks. The inner portion of the outflow is traced by dim 1.64 um [Feii] emission. The full extent of this outflow is at least 1,500" (about 10 pc in projection at a distance of 1.4 kpc). We speculate about the conditions responsible for the production of the ultra-fast jet and the absence of prominent large-scale molecular outflow lobes.