  We discuss the universality and self-similarity of void density profiles, for
voids in realistic mock luminous red galaxy (LRG) catalogues from the Jubilee
simulation, as well as in void catalogues constructed from the SDSS LRG and
Main Galaxy samples. Voids are identified using a modified version of the ZOBOV
watershed transform algorithm, with additional selection cuts. We find that
voids in simulation are self-similar, meaning that their average rescaled
profile does not depend on the void size, or -- within the range of the
simulated catalogue -- on the redshift. Comparison of the profiles obtained
from simulated and real voids shows an excellent match. The profiles of real
voids also show a universal behaviour over a wide range of galaxy luminosities,
number densities and redshifts. This points to a fundamental property of the
voids found by the watershed algorithm, which can be exploited in future
studies of voids.
