A new prescription for the spectral properties of population III stellar populations

TL;DR

This paper explores the spectral and emission properties of Population III stars during the Epoch of Reionization using the GALSEVN model, providing new diagnostics and insights into their role in reionization and gravitational wave signals.

Contribution

It introduces updated emission diagnostics effective for young Pop III populations and offers key quantities for modeling their impact on reionization and gravitational wave signals.

Findings

Emission-line diagnostics are effective for populations younger than ~1 Myr.

Provides estimates of ionizing photon production efficiency relevant for reionization.

Analyzes gravitational-wave signals from binary black hole mergers originating from Pop III stars.

Abstract

We investigated various emission properties of extremely low metallicity stellar populations in the Epoch of Reionization (EoR), using the new GALSEVN model, which has shown promising agreement between spectral predictions and observations at lower redshifts and higher metallicities. We find that emission-line diagnostics previously proposed to discriminate between population III (Pop III) stars and other primordial ionizing sources are effective, but only for stellar-population ages below $\sim1$ Myr. We provide other key quantities relevant to modeling Pop III stellar populations in the EoR, such as the production efficiency of ionizing photons, which is critical for reionization studies, the production rate of Lyman-Werner photons, which can dissociate H$_2$ and influence the efficiency of star formation, and the rates of different types of supernov\ae, offering insights into the timescales of chemical enrichment in metal-poor environments. We complement our study with a self-consistent investigation of the gravitational-wave signals generated by the mergers of binary black holes that formed through stellar evolution and their detectability. The results presented here provide valuable predictions for the study of the EoR, on the crucial role of low-metallicity stellar populations in reionization mechanisms and star formation, as well as meaningful insights into potential observational counterparts to direct detections of Pop III stars.