Merging groups and clusters of galaxies from the SDSS data. The
  catalogue of groups and potentially merging systems
  Galaxy groups and clusters are the main tools used to test cosmological
models and to study the environmental effect of galaxy formation. This work
provides a catalogue of galaxy groups and clusters, as well as potentially
merging systems based on the SDSS main galaxy survey. We identified galaxy
groups and clusters using the modified friends-of-friends (FoF) group finder
designed specifically for flux-limited galaxy surveys. The FoF group membership
is refined by multimodality analysis to find subgroups and by using the group
virial radius and escape velocity to expose unbound galaxies. We look for
merging systems by comparing distances between group centres with group radii.
  The analysis results in a catalogue of 88662 galaxy groups with at least two
members. Among them are 6873 systems with at least six members which we
consider to be more reliable groups. We find 498 group mergers with up to six
groups. We performed a brief comparison with some known clusters in the nearby
Universe, including the Coma cluster and Abell 1750. The Coma cluster in our
catalogue is a merging system with six distinguishable subcomponents. In the
case of Abell 1750 we find a clear sign of filamentary infall toward this
cluster. Our analysis of mass-to-light ratio (M/L) of galaxy groups reveals
that M/L slightly increases with group richness.
