  A new luminosity function for galaxies can be built starting from the product
of two random variables X and Y represented by a gamma variate with argument 2
>. The mean, the standard deviation and the distribution function of this new
distribution are computed. This new probability density function is assumed to
describe the mass distribution of galaxies. Through a non linear rule of
conversion from mass to luminosity a second new luminosity function for
galaxies is derived. The test of reliability of these two luminosity functions
was made on the Sloan Digital Sky Survey (SDSS) in five different bands. The
Schechter function gives a better fit with respect to the two new luminosity
functions for galaxies here derived.
