FOREVER22: The first bright galaxies with population III stars at redshifts z ≈ 10-20 and comparisons with JWST data
We study the formation of the first galaxies in overdense regions modelled by the FOREVER22 simulation project. Our simulations successfully reproduce the star formation rates and the MUV - Mstar relations of candidate galaxies at z ~ 10 - 14 observed by James Webb Space Telescope (JWST). We suggest that the observed galaxies are hosted by dark-matter haloes with Mh ≳ 1010 M⊙andareinshort- periodstarburstphases.Ontheotherhand,evensimulatedmassivegalaxiesinoverdenseregionscannotreproducetheintensestarformationratesandthelargestellarmassesofobservedcandidatesatz~ 16. Also, we show that the contribution of population III stars to the UV flux decreases as the stellar mass increases and it is a few per cent for galaxies with Mstar ~ 107 M⊙.Therefore,apartoftheobservedfluxbyJWSTcouldbethelightfrompopulationIIIstars.OursimulationssuggestthattheUVfluxcanbedominatedbypopulationIIIstarsandtheUV- slopeshowsβ ≲ -3 if future observations would reach galaxies with Mstars ~ 105 M⊙atz~ 20 of which the mass fraction of population III stars can be greater than 10 per cent.