Grids of stellar models with rotation: V. Models from 1.7 to 120 Msun at zero metallicity

TL;DR

This paper presents a comprehensive grid of zero-metallicity stellar models from 1.7 to 120 solar masses, highlighting how rotation influences their evolution, surface properties, and metal enrichment, with implications for understanding the first stars.

Contribution

The study provides the first extensive grid of rotating and non-rotating Population III stellar models across a wide mass range, emphasizing the effects of rotation on early star evolution.

Findings

Rotation increases core size and H-shell strength.

Massive rotating models reach critical rotation and lose mass.

Rotation affects metal enrichment, sometimes reducing it.

Abstract

Understanding the nature of the first stars is key to understanding the early universe. With new facilities such as JWST we may soon have the first observations of the earliest stellar populations, but to understand these observations we require detailed theoretical models. Here we compute a grid of stellar evolution models using the Geneva code with the aim to improve our understanding of the evolution of zero-metallicity stars, with particular interest in how rotation affects surface properties, interior structure, and metal enrichment. We produce a range of models of initial masses (Mini) from 1.7 Msun to 120 Msun, focusing on massive models of 9 Msun < Mini < 120 Msun. Our grid includes models with and without rotation, with rotating models having an initial velocity of 40% of the critical velocity. We find that rotation strongly impacts the evolution of the first stars, mainly through increased core size and stronger H-burning shells during core He-burning. Without radiative mass loss, angular momentum builds at the surface in rotating models, thus models of initial masses Mini > 60 Msun reach critical rotation on the main sequence and experience mass loss. We find that rotational mixing strongly affects metal enrichment, but does not always increase metal production as we see at higher metallicities. This is because rotation leads to an earlier CNO boost to the H shell during He-burning, which may hinder metal enrichment depending on initial mass and rotational velocity. Electronic tables of this new grid of Population III models are publicly available.