  We derive the number density evolution of massive field galaxies in the
redshift range 0.4 < z < 1.2 using the K-band selected field galaxy sample from
the Munich Near-IR Cluster Survey (MUNICS). We rely on spectroscopically
calibrated photometric redshifts to determine distances and absolute magnitudes
in the rest-frame K-band. To assign mass-to-light ratios, we use an approach
which maximizes the stellar mass for any K-band luminosity at any redshift. We
take the mass-to-light ratio, M/L_K, of a Simple Stellar Population (SSP) which
is as old as the universe at the galaxy's redshift as a likely upper limit.
This is the most extreme case of pure luminosity evolution and in a more
realistic model M/L_K will probably decrease faster with redshift due to
increased star formation. We compute the number density of galaxies more
massive than 2 10^10 h^-2 solar masses, 5 10^10 h^-2 solar masses, and 1 10^11
h^-2 solar masses, finding that the integrated stellar mass function is roughly
constant for the lowest mass limit and that it decreases with redshift by a
factor of roughly 3 and by a factor of roughly 6 for the two higher mass
limits, respectively. This finding is in qualitative agreement with models of
hierarchical galaxy formation, which predict that the number density of ~ M*
objects is fairly constant while it decreases faster for more massive systems
over the redshift range our data probe.
