The Mass Distribution of Population III Stars

TL;DR

This study analyzes the mass distribution of Population III stars using metal-poor star abundances, revealing a power-law initial mass function with a maximum mass around 87 solar masses, similar to present-day massive stars.

Contribution

It infers the initial mass function of Population III stars from observed metal-poor stars, providing new constraints on their mass range and distribution.

Findings

IMF well-described by a power law with exponent ~2.35

Maximum progenitor mass estimated at ~87 solar masses

No evidence for stars above ~120 solar masses

Abstract

Extremely metal-poor stars are uniquely informative on the nature of massive Population III stars. Modulo a few elements that vary with stellar evolution, the present-day photospheric abundances observed in extremely metal-poor stars are representative of their natal gas cloud composition. For this reason, the chemistry of extremely metal-poor stars closely reflects the nucleosynthetic yields of supernovae from massive Population III stars. Here we collate detailed abundances of 53 extremely metal-poor stars from the literature and infer the masses of their Population III progenitors. We fit a simple initial mass function to a subset of 29 of theinferred Population III star masses, and find that the mass distribution is well-represented by a power law IMF with exponent $\alpha = 2.35^{+0.29}_{-0.24}$. The inferred maximum progenitor mass for supernovae from massive Population III stars is $M_{\rm{max}} = 87^{+13}_{-33}$ M$_\odot$, and we find no evidence in our sample for a contribution from stars with masses above $\sim$120 M$_\odot$. The minimum mass is strongly consistent with the theoretical lower mass limit for Population III supernovae. We conclude that the IMF for massive Population III stars is consistent with the initial mass function of present-day massive stars and there may well have formed stars much below the supernova mass limit that could have survived to the present day.