The Highly Collimated Radio Jet of HH 80-81: Structure and Non-Thermal Emission

TL;DR

This paper presents high-resolution radio observations of the HH 80-81 jet, revealing detailed structure and confirming synchrotron emission from relativistic particles, indicating active particle acceleration at jet termination points.

Contribution

It provides the first high-sensitivity, high-resolution spectral index maps of HH 80-81, demonstrating the presence of non-thermal synchrotron emission and identifying shock regions as acceleration sites.

Findings

Synchrotron emission originates from extended jet components.

Termination points of the jet show strong shocks and particle acceleration.

High-resolution maps improve understanding of emission mechanisms.

Abstract

Radio emission from protostellar jets is usually dominated by free-free emission from thermal electrons. However, in some cases, it has been proposed that non-thermal emission could also be present. This additional contribution from non-thermal emission has been inferred through negative spectral indices at centimeter wavelengths in some regions of the radio jets. In the case of HH 80-81, one of the most powerful protostellar jets known, linearly polarized emission has also been detected, revealing that the non-thermal emission is of synchrotron nature from a population of relativistic particles in the jet. This result implies that an acceleration mechanism should be taking place in some parts of the jet. Here, we present new high sensitivity and high angular resolution radio observations at several wavelengths (in the 3-20 cm range) of the HH80-81 radio jet. These new observations represent an improvement in sensitivity and angular resolution by a factor of $\sim$10 with respect to previous observations. This allows us to resolve the morphology of the radio jet, and to study the different emission mechanisms involved through spectral index maps. We conclude that synchrotron emission in this jet arises from an extended component detected at low frequencies and from the termination points of the jet, where strong shocks against the ambient medium can produce efficient particle acceleration.