  Several observational studies and numerical simulations suggest that mergers
must contribute to the evolution of galaxies; however, the role that they play
is not yet fully understood. In this paper we study a sample of 52 double
nucleus disk galaxies that are considered as candidates for a minor merger
event. The luminosity of each of the nuclei and their relative separation are
derived from a multi-component photometric fit of the galaxies in the Sloan
Digital Sky Survey optical images. We find that the nuclei in most of the
sources have projected separations $\leq$ 4 kpc. The ratio of nuclear
luminosities indicates that most of the systems are likely in the coalescence
stage of a major merger. This is supported by the existence of a single galaxy
disk in 65% of the systems studied and the finding of a correlation between
nuclear luminosity and host luminosity for the single-disk systems: those
sources fitted with as single disk are in a more evolved stage of the merger
and present an enhancement of the nuclear luminosity compared to the
double-disk systems, as expected from simulations of galaxy mergers. Finally,
we identify a sample of 19 double nucleus disk galaxies in which the two nuclei
are physically separated by $\leq1$ kpc and constitute thus a sample of sub-kpc
binary AGN candidates.
