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 , \mathcal { 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 \mathcal { 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 \times 10 ^ { 10 } h ^ { -2 } \mathcal { M } _ { \odot } , 5 \times 10 ^ { 10 } h ^ { -2 } \mathcal { M } _ { \odot } , and 1 \times 10 ^ { 11 } h ^ { -2 } \mathcal { M } _ { \odot } , 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 \sim 3 and by a factor of \sim 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 \sim M ^ { * } objects is fairly constant while it decreases faster for more massive systems over the redshift range our data probe .