# Measuring the ionisation fraction in a jet from a massive protostar

## TL;DR

This study measures the ionisation fraction in a jet from a massive protostar, finding it similar to lower-mass stars, supporting a unified shock ionisation mechanism across different stellar masses.

## Contribution

It provides the first measurement of ionisation fraction in a massive protostar jet, demonstrating similarity with lower-mass star jets and supporting universal jet formation processes.

## Key findings

- Ionisation fraction in the jet is approximately 5-12%.
- Jet ionisation mechanisms are consistent across a wide range of stellar masses.
- Supports the idea of a common shock ionisation process in protostellar jets.

## Abstract

It is important to determine if massive stars form via disc accretion, like their low-mass counterparts. Theory and observation indicate that protostellar jets are a natural consequence of accretion discs and are likely to be crucial for removing angular momentum during the collapse. However, massive protostars are typically rarer, more distant and more dust enshrouded, making observational studies of their jets more challenging. A fundamental question is whether the degree of ionisation in jets is similar across the mass spectrum. Here we determine an ionisation fraction of $\sim5-12\%$ in the jet from the massive protostar G35.20-0.74N, based on spatially coincident infrared and radio emission. This is similar to the values found in jets from lower-mass young stars, implying a unified mechanism of shock ionisation applies in jets across most of the protostellar mass spectrum, up to at least $\sim10$ solar masses.