Simulations of Protostar-Driven Photoionization in Herbig-Haro Jets

TL;DR

This study uses axisymmetric MHD simulations to investigate how X-ray photoionization from young stars affects the ionization levels in Herbig-Haro jets, showing significant ionization near the star.

Contribution

It introduces the first detailed MHD simulations including X-ray photoionization effects on jet ionization in YSO environments.

Findings

X-ray photoionization can ionize 10-20% of the jet near the star.

Simulations suggest photoionization significantly influences jet ionization structure.

Photoionization effects are consistent with observed line emissions in YSO jets.

Abstract

Recent studies showed that observations of line emission from shocks in YSO jets require a substantial amount of ionization of the pre-shock matter. Photoionization from X-ray emitted close to the central source may be responsible for the initial ionization fraction. The aim of our work is to study the effect of X-ray photoionization, coming from the vicinity of the central star, on the ionization fraction inside the jet that can be advected at large distances. For this purpose we have performed axisymmetric MHD jet launching simulations including photoionization and optically thin losses using PLUTO. For typical X-ray luminosities in classical T-Tauri stars, we see that the photoionization is responsible for ionizing to 10 % -20 % the jet close to the star.