  Spherically symmetric dark energy structures are investigated in the
framework of a generalized Chaplygin gas (GCG), which has an equation of state
of the form $P = - A/\rho^{\alpha}} $. We also study these in a modified GCG
equation of state, which includes a matter term, i.e. $P = \sigma^{2} \rho -
A/\rho^{\alpha}$. The results of the latter are then compared with some
observational data on low-surface-brightness galaxies which are supposed to be
dominated by dark matter.
