# Massive star formation via torus accretion: the effect of photoionization feedback

## TL;DR

This study uses radiative hydrodynamic simulations to explore how photoionization feedback influences massive star formation via disk and torus accretion, revealing conditions that either trap or expand ionized regions, affecting star growth.

## Contribution

It provides new insights into the role of ionizing radiation in massive star formation, highlighting the impact of trapped versus expanding HII regions on accretion processes.

## Key findings

- Trapped HII regions permit continued accretion.
- Expanding HII regions disrupt the accretion torus.
- Critical conditions determine whether ionization halts or allows star growth.

## Abstract

The formation of massive stars is a long standing problem. Although a number of theories of massive star formation exist, ideas appear to converge to a disk-mediated accretion scenario. Here we present radiative hydrodynamic simulations of a star accreting mass via a disk embedded in a torus. We use a Monte Carlo based radiation hydrodynamics code to investigate the impact that ionizing radiation has on the torus. Ionized regions in the torus midplane are found to be either gravitationally trapped or in pressure driven expansion depending on whether or not the size of the ionized region exceeds a critical radius. Trapped Hii regions in the torus plane allow accretion to progress, while expanding Hii regions disrupt the accretion torus preventing the central star from aggregating more mass, thereby setting the star's final mass. We obtain constraints for the luminosities and torus densities that lead to both scenarios.