The VLA Nascent Disk And Multiplicity Survey of Perseus Protostars (VANDAM). III. Extended Radio Emission from Protostars in Perseus

TL;DR

This study uses high-resolution radio observations of Perseus protostars to analyze extended emission, revealing free-free and synchrotron emission in jets, which informs understanding of protostellar outflows and disk chemistry.

Contribution

It provides detailed spectral index analysis of protostellar jets, identifying synchrotron emission and jet misalignments, advancing knowledge of outflow mechanisms.

Findings

Spectral indices indicate free-free thermal emission in protostellar jets.

Detection of synchrotron emission suggests high-energy electrons are produced near disks.

Some jets are misaligned, implying complex outflow structures.

Abstract

Centimeter continuum emission from protostars offers insight into the innermost part of the outflows, as shock-ionized gas produces free-free emission. We observed a complete population of Class 0 and I protostars in the Perseus molecular cloud at 4.1 cm and 6.4 cm with resolution and sensitivity superior to previous surveys. From a total of 71 detections, 8 sources exhibit resolved emission at 4.1 cm and/or 6.4 cm. In this paper we focus on this sub-sample, analyzing their spectral indices along the jet, and their alignment with respect to the large-scale molecular outflow. Spectral indices for fluxes integrated toward the position of the protostar are consistent with free-free thermal emission. The value of the spectral index along a radio jet decreases with distance from the protostar. For six sources, emission is well aligned with the outflow central axis, showing that we observe the ionized base of the jet. This is not the case for two sources, where we note misalignment of the emission with respect to the large-scale outflow. This might indicate that the emission does not originate in the radio jet, but rather in an ionized outflow cavity wall or disk surface. For five of the sources, the spectral indices along the jet decrease well below the thermal free-free limit of -0.1 with $>2\sigma$ significance. This is indicative of synchrotron emission, meaning that high energy electrons are being produced in the outflows close to the disk. This result can have far-reaching implications for the chemical composition of the embedded disks.