  We study the impact of early dark energy (EDE) cosmologies on galaxy
properties by coupling high-resolution numerical simulations with semi-analytic
modeling (SAM) of galaxy formation and evolution. EDE models are characterized
by a non-vanishing high-redshift contribution of dark energy, producing an
earlier growth of structures and a modification of large-scale structure
evolution. They can be viewed as typical representatives of non-standard dark
energy models in which only the expansion history is modified, and hence the
impact on galaxy formation is indirect. We show that in EDE cosmologies the
predicted space density of galaxies is enhanced at all scales with respect to
the standard LCDM scenario, and the corresponding cosmic star formation history
and stellar mass density is increased at high-redshift. We compare these
results with a set of theoretical predictions obtained with alternative SAMs
applied to our reference LCDM simulation, yielding a rough measure of the
systematic uncertainty of the models. We find that the modifications in galaxy
properties induced by EDE cosmologies are of the same order of magnitude as
intra-SAM variations for a standard LCDM realization (unless rather extreme EDE
models are considered), suggesting that is difficult to use such predictions
alone to disentangle between different cosmological scenarios. However, when
independent information on the underlying properties of host dark matter haloes
is included, the SAM predictions on galaxy bias may provide important clues on
the expansion history and the equation-of-state evolution.
