  This paper presents the results of simulated NGST observations. The goal of
this work is to study the detectability of very high redshift galaxies and to
try to characterize Wide Deep-Field observations. The main points made in this
paper are 1) high-z galaxies observable by NGST would be similar to local
starburst galaxies 2) even if they exist, large spiral galaxies similar to
local ones would not be observed by a NGST-like telescope and 3) the density of
high-z galaxies detected so far is apparently moderate.
