Pure luminosity evolution models for faint field galaxy samples

We have examined a set of pure luminosity evolution (PLE) models in order toexplore up to what extent the rapidly increasing observational constraints fromfaint galaxy samples can be understood in this simple framework. We find that aPLE model, in which galaxies evolve mildly in time even in the rest frame UV,can reproduce most of the observed properties of faint galaxies assuming anopen ($\Omega\sim0$) universe. In particular, such a model is able to fitreasonably well the number counts in the $U,~b_j,~r_f,~I$, and $K$ bands, aswell as the colour and redshift distributions derived from most of the existingsamples. The most significant discrepancy between the predictions of this modeland the data is the $z$ distribution of faint $K$-selected galaxies.Significantly worse fits are obtained with PLE models for the theoreticallyattractive value of $\Omega = 1$, although a simple number luminosity evolutionmodel with a significant amount of merger events fits the data also in thiscosmology.Comment: 15 pages, plain tex (insert encapsulated postscript figures), plus an extra figure Fig3c.ps and the tex-macro mn.tex uuencoded, gzipp'ed tar file -- accepted by MNRA