Two Populations of Open Star Clusters in the Galaxy
  Based on our compiled catalogue of fundamental astrophysical parameters for
593 open clusters, we analyze the relations between the chemical composition,
spatial positions, Galactic orbital elements, age, and other physical
parameters of open star clusters. We show that the population of open clusters
is heterogeneous and is divided into two groups differing by their mean
parameters, properties, and origin. One group includes the Galactic clusters
formed mainly from the interstellar matter of the thin disk with nearly solar
metallicities ([Fe/H] > -0.2) and having almost circular orbits a short
distance away from the Galactic plane, i.e., typical of the field stars of the
Galactic thin disk. The second group includes the peculiar clusters formed
through the interaction of extragalactic objects (such as high--velocity
clouds, globular clusters, or dwarf galaxies) with the interstellar matter of
the thin disk, which, as a result, derived abnormally low (for field thin-disk
stars) metallicities and/or Galactic orbits typical of objects of the older
Galactic subsystems.
