Unveiling the contribution of Pop III stars in primeval galaxies at redshift $\geq 6$

TL;DR

This study models the contribution of Pop III stars to early galaxies at redshifts 6 to 30 using a semi-analytical approach, predicting their detectability with JWST and implications for understanding the first stars.

Contribution

It provides the first comprehensive analysis of Pop III stars' role across a wide range of halo masses and redshifts, informing future JWST observations.

Findings

Pop III stars dominate in low-mass halos of 10^7-10^9 M_sun.

Galaxies with stellar mass 10^9 M_sun can exist as early as z~30.

Pop III-dominated galaxies are too faint for direct JWST detection.

Abstract

Detection of the first stars has remained elusive so-far but their presence may soon be unveiled by upcoming JWST observations. Previous studies have not investigated the entire possible range of halo masses and redshifts which may help in their detection. Motivated by the prospects of detecting galaxies up to $z\sim 20$ in JWST early data release, we quantify the contribution of Pop III stars to high-redshift galaxies from $6 \leq z \leq 30$ by employing the semi-analytical model A-SLOTH, which self-consistently models the formation of Pop III and Pop II stars along with their feedback. Our results suggest that the contribution of Pop III stars is the highest in low-mass halos of $\rm 10^7-10^9~M_{\odot}$. While high-mass halos $\rm \geq 10^{10}~M_{\odot}$ contain less than 1\% Pop III stars, they host galaxies with stellar masses of $\rm 10^9~M_{\odot}$ as early as $z \sim 30$. Interestingly, the apparent magnitude of Pop~III populations gets brighter towards higher redshift due to the higher stellar masses, but Pop~III-dominated galaxies are too faint to be directly detected with JWST. Our results predict JWST can detect galaxies up to $z\sim 30$, which may help in constraining the IMF of Pop III stars and will guide observers to discern the contribution of Pop~III stars to high-redshift galaxies.