Radio spectra of protostellar jets: Thermal and non-thermal emission

TL;DR

This paper presents a numerical model of protostellar jets that combines thermal free-free and non-thermal synchrotron emission mechanisms, analyzing how various parameters influence radio spectra and emission processes.

Contribution

It introduces a comprehensive model that incorporates both thermal and non-thermal emission in protostellar jets, accounting for jet geometry and ionization variations.

Findings

Radio emission depends on jet parameters and viewing angle.

Spectral indices vary with ionization and emission mechanisms.

Turnover frequencies are influenced by jet interactions with the interstellar medium.

Abstract

Protostellar jets and outflows are pointers of star-formation and serve as important sources of momentum and energy transfer to the interstellar medium. Radio emission from ionized jets have been detected towards a number of protostellar objects. In few cases, negative spectral indices and polarized emission have also been observed suggesting the presence of synchrotron emission from relativistic electrons. In this work, we develop a numerical model that incorporates both thermal free-free and non-thermal synchrotron emission mechanisms in the jet geometry. The flux densities include contribution from an inner thermal jet, and a combination of emission from thermal and non-thermal distributions along the edges and extremities, where the jet interacts with the interstellar medium. We also include the effect of varying ionization fraction laterally across the jet. An investigation of radio emission and spectra along the jet shows the dependence of the emission process and optical depth along the line of sight. We explore the effect of various parameters on the turnover frequencies and the radio spectral indices (between 10 MHz and 300 GHz) associated with them.