Unveiling the Contribution of Population III Stars in Primeval Galaxies at Redshift ≥6

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 that may help in their detection. Motivated by the prospects of detecting galaxies up to z ∼ 20 in the JWST early data release, we quantify the contribution of Population III stars to high-redshift galaxies from 6 ≤ z ≤ 30 by employing the semianalytical model a-sloth, which self-consistently models the formation of Population III and Population II stars along with their feedback. Our results suggest that the contribution of Population III stars is the highest in low-mass halos of 107–109 M ⊙. While high-mass halos ≥1010 M ⊙ contain less than 1% Population III stars, they host galaxies with stellar masses of 109 M ⊙ as early as z ∼ 30. Interestingly, overall the apparent magnitude of Population III stars gets brighter toward higher redshift due to the higher stellar masses, but Population III–dominated galaxies are too faint to be directly detected with JWST. Our results predict JWST can detect galaxies up to z ∼ 30, which may help in constraining the initial mass function of Population III stars and will guide observers to discern the contribution of Population III stars to high-redshift galaxies.