  We have studied the appearance of vortex arrays in a rotating helium-4
nanodroplet at zero temperature within density functional theory. Our results
are compared with those for classical rotating fluid drops used to analyze the
shape and vorticity in recent experiments [L.F. Gomez et al., Science 345, 906
(2014)], where vortices have been directly seen in superfluid droplets for the
first time. In agreement with the experiments, we have found that the shape of
the droplet changes from pseudo-spheroid, oblate-like for a small number of
vortices to a peculiar "wheel-like" shape, delimited by nearly flat upper and
lower surfaces, when the number of vortices is large. Also in agreement with
the experiments, we have found that the droplet remains stable well above the
stability limit predicted by classical theories.
