The Impact of Feedback in Massive Star Formation. II. Lower Star Formation Efficiency at Lower Metallicity

Kei E I Tanaka,Takashi Hosokawa,Jonathan C Tan,Yichen Zhang

doi:10.3847/1538-4357/aac892

Abstract

Abstract We conduct a theoretical study of the formation of massive stars over a wide range of metallicities from 10−5 to and evaluate the star formation efficiencies (SFEs) from prestellar cloud cores taking into account multiple feedback processes. Unlike for simple spherical accretion, feedback processes in the case of disk accretion do not set upper limits on stellar masses. At solar metallicity, launching of magneto-centrifugally driven outflows is the dominant feedback process to set SFEs, while radiation pressure, which has been regarded as pivotal, makes only a minor contribution even in the formation of stars over . Photoevaporation becomes significant in the formation of stars over at low metallicities of , where dust absorption of ionizing photons is inefficient. We conclude that if initial prestellar core properties are similar, then massive stars are rarer in extremely metal-poor environments of 10−5– . Our results give new insight into the high-mass end of the initial mass function and its potential variation with galactic and cosmological environments.

Highlights

Massive stars are the main sources of UV radiation, turbulent energy, and heavy elements
We conduct a theoretical study of the formation of massive stars over a wide range of metallicities from 10−5 to 1Z⊙ and evaluate the star formation efficiencies (SFEs) from prestellar cloud cores taking into account multiple feedback processes
It is important to understand how the massive star formation process depends on galactic environmental conditions, since this shapes the high-mass end of the initial mass function (IMF) and affects how the IMF may vary through cosmic history

Summary

Introduction

Massive stars are the main sources of UV radiation, turbulent energy, and heavy elements. It is important to understand how the massive star formation process depends on galactic environmental conditions, since this shapes the high-mass end of the initial mass function (IMF) and affects how the IMF may vary through cosmic history. To address this topic, we have developed a model of feedback during massive star formation relevant for solar metallicity conditions, especially star formation efficiencies from prestellar gas cores (Tanaka et al 2017b, hereafter Paper I). We apply this model to a wide range of metallicities that are expected to be relevant to galactic environments across most of the evolution of the universe

Methods

Results

Discussion

Conclusion