Color similarity study among small galaxy groups members
  We applied a membership test based on the color similarity of group members
to detect the discordant galaxies in small groups (quintets) that had been
determined by the Friends-of-Friends (FoF) algorithm. Our method depends on the
similarity of the color indices (u-g) and (g-r) of the group members. The
chosen sample of quintets was extracted from "Flux- and volume-limited groups
for SDSS galaxies" catalog which is a spectroscopic sample of galaxies
originally taken from the Sloan Digital Sky Survey - Data Release 10
(SDSS-DR10). The sample included 282 quintets with a total number of 1410
galaxies. The similarity measure used in this study is the Euclidean distance.
The calculations showed that 73.4% of the group samples (207 out of 282 quintet
groups) have galaxies with similar colors (u-g) and (g-r). Each of the
remainder groups (75 systems) has an interloper galaxy with different colors
than the other members, and hence they became quadrants. We found that group
members tend to be more luminous than outliers. We conclude that using the
similarities in the color indices between group members gives better
identification of group membership.
