Galaxy interactions in different environments: An analysis of galaxy
  pairs from the SDSS
  We analyze the galaxy pairs in a volume limited sample ($M_r \leq -21$) from
the SDSS to study the effects of galaxy interactions on the star formation rate
and colour of galaxies in different environments. We study the star formation
rate and colour of the paired galaxies as a function of projected separation
and compare the results with their control samples matched in stellar mass,
redshift and local density. We find that the major interactions significantly
enhance the star formation rate in paired galaxies and turn them bluer with
decreasing pair separation within $30$ kpc. The impact of tidal interactions on
star formation rate and colour are more significant in the heavier members of
the major pairs. The star formation enhancement in major pairs is significantly
higher at the low-density environments, where the influence can extend up to
$\sim 100$ kpc. Contrarily, the major pairs at high-density environments show
suppression in their star formation. Depending on the embedding environments,
the major interactions in the intrinsically brighter galaxy pairs can thus
enhance or quench star formation. We find that the minor pairs at both
low-density and high-density environments are significantly less star-forming
and redder than their control galaxies. It indicates that the minor
interactions in intrinsically brighter galaxy pairs always suppress the star
formation irrespective of their environment. The lighter members in these minor
pairs show a greater susceptibility to suppressed star formation. Our results
imply that both the major and minor interactions can contribute to the observed
bimodality. We conclude that the galaxy evolution is determined by a complex
interplay between the galaxy properties, galaxy interactions, and environment.
