Growth of First Galaxies: Impacts of Star Formation and Stellar Feedback

Recent observations have detected galaxies at high-redshift $z\sim 6\text{--}11$, and revealed the diversity of their physical properties, from normal star-forming galaxies to starburst galaxies. To understand the properties of these observed galaxies, it is crucial to understand the star formation (SF) history of high-redshift galaxies under the influence of stellar feedback. In this work, we present the results of cosmological hydrodynamic simulations with zoom-in initial conditions, and investigate the formation of the first galaxies and their evolution toward observable galaxies at $z\sim 6$. We focus on three different galaxies that end up in halos with masses $M_h=2.4\times {10}^{10}{h}^{-1}{M}_{\odot }$ (Halo-10), $1.6\times {10}^{11}{h}^{-1}{M}_{\odot }$ (Halo-11), and $0.7\times {10}^{12}{h}^{-1}{M}_{\odot }$ (Halo-12) at z = 6. Our simulations also probe the impacts of different subgrid assumptions, i.e., SF efficiency and cosmic reionization, on SF histories in the first galaxies. We find that SF occurs intermittently due to supernova (SN) feedback at $z\gtrsim 10$, and then it proceeds more smoothly as the halo mass grows at lower redshifts. Galactic disks are destroyed due to SN feedback, while galaxies in simulations with no feedback or lower SF efficiency models can sustain a galactic disk for long periods $\gtrsim 10Myr$. The expulsion of gas at the galactic center also affects the inner dark matter density profile for a short period. Our simulated galaxies in Halo-11 and Halo-12 reproduce the SF rates and stellar masses of observed Lyα emitters at $z\sim 7\text{--}8$ fairly well given the observational uncertainties.