Resolving the collimation zone of an intermediate-mass protostar

TL;DR

This study provides high-resolution multi-frequency observations of an intermediate-mass protostar, revealing detailed jet structures, episodic velocity variations, and a coexistence of collimated jets and wide-angle winds, advancing understanding of star formation processes.

Contribution

First multi-epoch, multi-frequency imaging of an intermediate-mass YSO's innermost regions, revealing jet collimation, episodic ejections, and wind coexistence with implications for star formation models.

Findings

Highly collimated ionized stream launched at ~0.4 au

Narrow ionized cavity excited by wide-angle wind

Jet exhibits episodic velocity variations

Abstract

We report new VLA and e-MERLIN high resolution and sensitivity images of the Triple Radio continuum Source in the Serpens star forming region. These observations allowed us to perform a deep multi-frequency, multi-epoch study by exploring the innermost regions (<~100 au) of an intermediate-mass YSO for the first time, with a physical resolution of ~15 au. The kinematic analysis of knots recently ejected by the protostar indicates that the jet is undergoing episodic variations in velocity. In addition, our multi-frequency images reveal striking characteristics, e.g., a highly collimated ionized stream that would be launched at a radial distance of ~0.4 au from the protostar, and a narrow (~28 au wide) ionized cavity that would be excited by the interaction of a wide-angle component with the surrounding toroid of infalling material. In light of these results, we propose the scenario in which both a highly-collimated jet and a wide-angle wind coexist to be the most plausible to explain our observations, either launched by the X-wind or X- plus Disk-wind mechanism.