The First Stars: A Low-Mass Formation Mode

TL;DR

This study uses detailed numerical simulations to explore the formation of low-mass Population III stars, revealing a unique star formation mode with potential long-lived, surviving stars enriched by AGB mass transfer.

Contribution

It presents the first detailed simulation of low-mass Population III star formation under feedback, showing a distinct formation pathway with implications for surviving ancient stars.

Findings

Stars in this system reach masses up to 5 solar masses.

The star formation rate is unusually low compared to earlier minihalos.

Potential existence of surviving Population III stars enriched by AGB companions.

Abstract

We perform numerical simulations of the growth of a Population III stellar system under photodissociating feedback. We start from cosmological initial conditions at z = 100, self-consistently following the formation of a minihalo at z = 15 and the subsequent collapse of its central gas to high densities. The simulations resolve scales as small as ~ 1 AU, corresponding to gas densities of 10^16 cm^-3. Using sink particles to represent the growing protostars, we evolve the stellar system for the next 5000 years. We find that this emerging stellar group accretes at an unusually low rate compared with minihalos which form at earlier times (z = 20 - 30), or with lower baryonic angular momentum. The stars in this unusual system will likely reach masses ranging from < 1 M_sun to 5 M_sun by the end of their main-sequence lifetimes, placing them in the mass range for which stars will undergo an asymptotic giant branch (AGB) phase. Based upon the simulation, we predict the rare existence of Population III stars that have survived to the present day and have been enriched by mass overflow from a previous AGB companion.