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The evolution of halos with masses around Mₕ 10^11\; M_ and Mₕ 10^12\; M_ at redshifts z>9 is examined using constrained N-body simulations. The specific mass accretion rates, Ṁₕ / Mₕ, exhibit minimal mass dependence and agree with existing literature. Approximately one-third of simulations reveal an increase in Ṁₕ around z 13, possibly implying a dual-age stellar population. Comparing simulated halos with observed galaxies having spectroscopic redshifts, we find that for galaxies at z9, the ratio between observed star formation rate (SFR) and Ṁₕ is approximately 2\%. This ratio remains consistent for the stellar-to-halo mass ratio (SHMR) but only for z10. At z 9, the SHMR is notably lower by a factor of a few. At z10, there is an agreement between specific star formation rates (sSFRs) and Ṁₕ / Mₕ of halos. However, at z 9, observed sSFRs exceed simulated values by a factor of two. To explain the relatively high star formation efficiencies in high-z halos with Mₕ 10^11 M_, a simplified model is proposed, assuming the applicability of the local Kennicutt-Schmidt law. The enhanced efficiency relative to low-z is mainly driven by the reduced effectiveness of stellar feedback due to deeper gravitational potential for halos of a fixed mass.
Adi Nusser (Thu,) studied this question.