This paper investigates the first emergence of cold accretion, where accretion flows deeply penetrate a halo, in the early universe using cosmological N-body/SPH simulations. The study focuses on small halos (10⁸ M⊙) with high spatial resolution (∼1 pc). Unlike previous studies with short observation periods, this research tracks long-term evolution until cold accretion appears, employing the sink particle method. The findings establish a minimum halo mass for cold accretion emergence and explore whether this process generates dense shock waves conducive to supermassive star (SMS) formation. Simulations reveal dense shocks created when the accretion flow impacts a compact disc, resulting in dense, hot post-shock gas suitable for gravitational collapse and subsequent SMS formation.

Masaki Kiyuna, Takashi Hosokawa, Sunmyon Chon