We have constructed a morphologically divided redshift distribution of faint field galaxies using a statistically unbiased sample of 196 galaxies brighter than I = 21.5 for which detailed morphological information ( from the Hubble Space Telescope ) as well as ground-based spectroscopic redshifts are available .
Galaxies are classified into 3 rough morphological types according to their visual appearance ( E/S0s , Spirals , Sdm/dE/Irr/Pec ’ s ) , and redshift distributions are constructed for each type .
The most striking feature is the abundance of low to moderate redshift Sdm/dE/Irr/Pec ’ s at I < 19.5 .
This confirms that the faint end slope of the luminosity function ( LF ) is steep ( \alpha < -1.4 ) for these objects .
We also find that Sdm/dE/Irr/Pec ’ s are fairly abundant at moderate redshifts , and this can be explained by strong luminosity evolution .
However , the normalization factor ( or the number density ) of the LF of Sdm/dE/Irr/Pec ’ s is not much higher than that of the local LF of Sdm/dE/Irr/Pec ’ s .
Furthermore , as we go to fainter magnitudes , the abundance of moderate to high redshift Irr/Pec ’ s increases considerably .
This can not be explained by strong luminosity evolution of the dwarf galaxy populations alone : these Irr/Pec ’ s are probably the progenitors of present day ellipticals and spiral galaxies which are undergoing rapid star formation or merging with their neighbors .
On the other hand , the redshift distributions of E/S0s and spirals are fairly consistent those expected from passive luminosity evolution , and are only in slight disagreement with the non-evolving model .