The most massive Population III stars

TL;DR

This paper develops a statistical framework to estimate the maximum masses of Population III stars at high redshifts, suggesting they could be extremely massive and serve as seeds for supermassive black holes.

Contribution

It introduces an extreme-value statistical model to predict the upper mass limits of Pop III stars based on star formation rates and efficiencies.

Findings

Most massive Pop III stars likely exceed 10^3-10^4 solar masses.

Such stars could be progenitors of supermassive black holes.

The model constrains the stellar initial mass function at early cosmic times.

Abstract

Recent data from the James Webb Space Telescope suggest that there are realistic prospects for detecting the earliest generation of stars at redshift ~20. These metal-poor, gaseous Population III (Pop III) stars are likely in the mass range 10-1000 solar masses. We develop a framework for calculating the abundances of Pop III stars as well as the distribution of the most massive Pop III stars based on an application of extreme-value statistics. Our calculations use the star formation rate density from a recent simulation to calibrate the star-formation efficiency from which the Pop III stellar abundances are derived. Our extreme-value modelling suggests that the most massive Pop III stars at redshifts 10-20 are likely to be $\gtrsim10^3-10^4\,{\rm M}_\odot$. Such extreme Pop III stars were sufficiently numerous to be the seeds of supermassive black holes at high redshifts and possibly source detectable gravitational waves. We conclude that the extreme-value formalism provides an effective way to constrain the stellar initial mass function.