The first galaxies: simulating their feedback-regulated assembly

TL;DR

This study uses detailed radiation-hydrodynamical simulations to explore the feedback-regulated formation of a low-mass galaxy at high redshift, highlighting the transition from Pop III to Pop II star formation and the effects of stellar feedback.

Contribution

It presents the first comprehensive simulation of a galaxy with $~10^8$ solar masses at z=10, including Pop III and Pop II star formation and various feedback mechanisms.

Findings

Pop III star formation dominates until z=13.

Galaxy's gas is fully metal-enriched, with no primordial pockets.

Predicted flux is too low for JWST detection without lensing.

Abstract

We investigate the formation of a galaxy reaching a virial mass of $~ 10^8$ solar mass at $z=10$ by carrying out a zoomed radiation-hydrodynamical cosmological simulation. This simulation traces Population~III (Pop~III) star formation, characterized by a modestly top-heavy initial mass function (IMF), and considers stellar feedback such as photoionization heating from Pop III and Population~II (Pop~II) stars, mechanical and chemical feedback from supernovae (SNe), and X-ray feedback from accreting black holes (BHs) and high-mass X-ray binaries (HMXBs). We self-consistently impose a transition in star formation mode from top-heavy Pop III to low-mass Pop~II, and find that the star formation rate in the computational box is dominated by Pop~III until $z=13$, and by Pop~II thereafter. The simulated galaxy experiences bursty star formation, with a substantially reduced gas content due to photoionization heating from Pop~III and Pop~II stars, together with SN feedback. All the gas within the simulated galaxy is metal-enriched above $10^{-5}$ solar, such that there are no remaining pockets of primordial gas. The simulated galaxy has an estimated observed flux of $~10^{-3} nJy$, which is too low to be detected by the James Webb Space Telescope (JWST) without strong lensing amplification. We also show that our simulated galaxy is similar in terms of stellar mass to Segue 2, the least luminous dwarf known in the Local Group.