A Cosmological Solution to the Impossibly Early Galaxy Problem
  To understand the formation and evolution of galaxies at redshifts z < 10,
one must invariably introduce specific models (e.g., for the star formation) in
order to fully interpret the data. Unfortunately, this tends to render the
analysis compliant to the theory and its assumptions, so consensus is still
somewhat elusive. Nonetheless, the surprisingly early appearance of massive
galaxies challenges the standard model, and the halo mass function estimated
from galaxy surveys at z > 4 appears to be inconsistent with the predictions of
LCDM, giving rise to what has been termed "The Impossibly Early Galaxy Problem"
by some workers in the field. A simple resolution to this question may not be
forthcoming. The situation with the halos themselves, however, is more
straightforward and, in this paper, we use linear perturbation theory to derive
the halo mass function over the redshift range z < 10 for the R_h=ct universe.
We use this predicted halo distribution to demonstrate that both its dependence
on mass and its very weak dependence on redshift are compatible with the data.
The difficulties with LCDM may eventually be overcome with refinements to the
underlying theory of star formation and galaxy evolution within the halos. For
now, however, we demonstrate that the unexpected early formation of structure
may also simply be due to an incorrect choice of the cosmology, rather than to
yet unknown astrophysical issues associated with the condensation of mass
fluctuations and subsequent galaxy formation.
