  An estimate for the number of ionizing photons per baryon as a function of
redshift is computed based on the plausible extrapolation of the observed
galaxy UV luminosity function and the latest results on the properties of the
escape fraction of ionizing radiation. It is found that, if the escape fraction
for low mass galaxies (Mtot<10^{11}Msun) is assumed to be negligibly small, as
indicated by numerical simulations, then there are not enough ionizing photons
to reionize the universe by z=6 for the cosmology favored by the WMAP 3rd year
results, while the WMAP 1st year cosmology is marginally consistent with the
reionization requirement. The escape fraction as a function of galaxy mass
would have to be constant to within a factor of two for the whole mass range of
galaxies for reionization to be possible within the WMAP 3rd year cosmology.
