Non-thermal Radio Emission from Massive Protostars in the SARAO MeerKAT Galactic Plane Survey

TL;DR

This study investigates non-thermal radio emission from massive protostars using MeerKAT data, revealing that at least half of the jets exhibit non-thermal radiation, advancing understanding of early stellar evolution.

Contribution

It provides the first large-scale survey of non-thermal radio emission from massive protostars, identifying a significant fraction of jets with non-thermal characteristics.

Findings

At least 50% of jets emit non-thermal radiation.

Detection rate of protostellar jets is 44%.

Extended sources show evidence of non-thermal emission.

Abstract

We present an investigation of the L-band emission from known massive young stellar objects (MYSOs) in the SARAO MeerKAT Galactic Plane Survey to search for non-thermal radio emitters in the sample. A total of 398 massive protostars, identified from the Red MSX Source (RMS) survey, are located within the survey region. Among these, 162 fields that host the protostars are isolated from nearby bright HII regions, allowing for the study of any ionized jets present. Seventy-one of these fields have jets with five-sigma detections or higher, corresponding to a detection rate of 44%. The MeerKAT fluxes of the detections, together with the upper limits of the non-detections and any other fluxes from previous observations, were used to estimate the spectral indices of the jets, and to search for the presence of non-thermal radiation. In cases where a source manifests as single in a given observation but is resolved into multiple components in observations of higher resolutions, the sum of the fluxes of the resolved components was used in estimating the indices. Any e!ects from missing flux in higher-resolution observations were incorporated into the index uncertainties. The spectral indices of the sample show that at least 50% of the jets emit non-thermal radiation. Additionally, the spectral energy distribution (SED) of some of the sources, as well as their radio luminosities exhibit evidence of non-thermal emission, especially in extended sources.