FOREVER22: The first bright galaxies with population III stars at redshifts z ≃ 10–20 and comparisons with JWST data
Hidenobu Yajima, Makito Abe, Hajime Fukushima, Yoshiaki Ono, Yuichi Harikane, Masami Ouchi, Takuya Hashimoto, Sadegh Khochfar- Space and Planetary Science
- Astronomy and Astrophysics
Abstract
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⊙ and are in short-period starburst phases. On the other hand, even simulated massive galaxies in overdense regions cannot reproduce the intense star formation rates and the large stellar masses of observed candidates at z ∼ 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, a part of the observed flux by JWST could be the light from population III stars. Our simulations suggest that the UV flux can be dominated by population III stars and the UV-slope shows β ≲ −3 if future observations would reach galaxies with Mstars ∼ 105 M⊙ at z ∼ 20 of which the mass fraction of population III stars can be greater than 10 per cent.