Grids of stellar models with rotation – V. Models from 1.7 to 120 M⊙ at zero metallicity

Abstract

ABSTRACT Understanding the nature of the first stars is key to understanding the early Universe. With new facilities such as James Webb Space Telescope (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 $1.7$ to $120\, \mathrm{M}_{\odot }$, focusing on massive models of $9 \le M_{\rm ini}\le 120\, \mathrm{M}_{\odot }$. Our grid includes models with and without rotation, with rotating models having an initial velocity of 40 per cent 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 $M_{\rm ini}\ge 60 \, \mathrm{M}_{\odot }$ 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.