  The common nature of dark matter and dark energy is argued in [1] based on
the approach that the cosmological constant \Lambda enters the weak-field
General Relativity following from Newton theorem on the "sphere-point mass"
equivalency [2]. Here we probe the \Lambda-gravity description of dark matter
in galaxy systems, from pairs up to galaxy clusters using the data of various
sources, i.e. of Local Supercluster galaxy surveys, gravity lensing and Planck
satellite. The prediction that the cosmological constant has to be the lower
limit for the weak-field \Lambda obtained from galaxy systems of various degree
of virialization is shown to be supported by those observations. The results
therefore support the \Lambda-gravity nature of dark matter in the studied
systems, implying that the positivity of the cosmological constant might be
deduced decades ago from the dynamics of galaxies and galaxy clusters far
before the cosmological SN surveys.
