  Aims: We estimate stellar masses of galaxies in the high redshift universe
with the intention of determining the influence of newly available Spitzer/IRAC
infrared data on the analysis. Based on the results, we probe the mass assembly
history of the universe.
  Methods: We use the GOODS-MUSIC catalog, which provides multiband photometry
from the U--filter to the 8 mum Spitzer band for almost 15,000 galaxies with
either spectroscopic (for ~7 % of the sample) or photometric redshifts, and
apply a standard model fitting technique to estimate stellar masses. We then
repeat our calculations with fixed photometric redshifts excluding Spitzer
photometry and directly compare the outcomes to look for systematic deviations.
Finally we use our results to compute stellar mass functions and mass densities
up to redshift z = 5.
  Results: We find that stellar masses tend to be overestimated on average if
further constraining Spitzer data are not included into the analysis. Whilst
this trend is small up to intermediate redshifts z < 2.5 and falls within the
typical error in mass, the deviation increases strongly for higher redshifts
and reaches a maximum of a factor of three at redshift z = 3.5. Thus, up to
intermediate redshifts, results for stellar mass density are in good agreement
with values taken from literature calculated without additional Spitzer
photometry. At higher redshifts, however, we find a systematic trend towards
lower mass densities if Spitzer/IRAC data are included.
