  We consider the possibility that the dark matter is coupled through its mass
to a scalar field associated with the dark energy of the Universe. In order for
such a field to play a role at the present cosmological distances, it must be
effectively massless at galactic length scales. We discuss the effects of the
field on the distribution of dark matter in galaxy halos. We show that the
profile of the distribution outside the galaxy core remains largely unaffected
and the approximately flat rotation curves persist. The dispersion of the dark
matter velocity is enhanced by a potentially large factor relative to the case
of zero coupling between dark energy and dark matter. The counting rates in
terrestrial dark matter detectors are similarly enhanced. Existing bounds on
the properties of dark matter candidates can be extended to the coupled case,
by taking into account the enhancement factor.
