Contributed Talk - Splinter Stars

Tuesday, 14 September 2021, 09:00   (virtual Stars)

On the metallicity-dependence of radiation forces and photoionization feedback in massive star formation

Zentrum für Astronomie der Universität Heidelberg

The formation of the most massive stars in the primordial and present-day Universe is hindered by the strong radiative feedback of the forming star itself. In Kuiper & Hosokawa (2018), we modeled the formation of a massive star from a collapsing cloud of dusty gas at solar metallicity, for the first time including the star's impact due to radiation forces and photoionization simultaneously. Here, we will report on our follow-up investigations of the effect of radiation forces and photoionization feedback in environments of different metallicity. While radiation forces were found to be responsible for stopping accretion onto the most massive stars in the present-day Universe, the relative impact of photoionization increases strongly toward environments of lower metallicity and ultimately dominate the stellar impact for metallicities approximately lower than 0.01 the solar value. This result from our direct numerical simulations of the star formation process agrees well with previous estimates using semi-analytical arguments. We conclude that the upper end of the initial mass function is crucially shaped by different forms of radiative feedback.