A redshift-independent efficiency model: star formation and stellar
  masses in dark matter halos at z>4
  We explore the connection between the UV luminosity functions (LFs) of
high-$z$ galaxies and the distribution of stellar masses and star-formation
histories (SFHs) in their host dark matter halos. We provide a baseline for a
redshift-independent star-formation efficiency model to which observations and
models can be compared. Our model assigns a star-formation rate (SFR) to each
dark matter halo based on the growth rate of the halo and a
redshift-independent star-formation efficiency. The dark matter halo accretion
rate is obtained from a high-resolution $N$-body simulation in order to capture
the stochasticity in accretion histories and to obtain spatial information for
the distribution of galaxies. The halo mass dependence of the star-formation
efficiency is calibrated at $z=4$ by requiring a match to the observed UV LF at
this redshift. The model then correctly predicts the observed UV LF at
$z=5-10$. We present predictions for the UV luminosity and stellar mass
functions, \textit{JWST} number counts, and SFHs. In particular, we find a
stellar-to-halo mass relation at $z=4-10$ that scales with halo mass at $M_{\rm
h}<10^{11}~M_{\odot}$ as $M_{\star}\propto M_{\rm h}^2$, with a normalization
that is higher than the relation inferred at $z=0$. The average SFRs increase
as a function of time to $z=4$, although there is significant scatter around
the average: about 6\% of the $z=4$ galaxies show no significant mass growth.
Using these SFHs, we present redshift-dependent UV-to-SFR conversion factors,
mass return fractions, and mass-to-light ratios for different intial mass
functions and metallicities, finding that current estimates of the cosmic SFR
density at $z\sim10$ may be overestimated by $\sim0.1-0.2~\mathrm{dex}$.
