Galaxy Zoo: The properties of merging galaxies in the nearby Universe -
  local environments, colours, masses, star-formation rates and AGN activity
  Following the study of Darg et al. (2009; hereafter D09a) we explore the
environments, optical colours, stellar masses, star formation and AGN activity
in a sample of 3003 pairs of merging galaxies drawn from the SDSS using visual
classifications from the Galaxy Zoo project. While D09a found that the
spiral-to-elliptical ratio in (major) mergers appeared higher than that of the
global galaxy population, no significant differences are found between the
environmental distributions of mergers and a randomly selected control sample.
This makes the high occurrence of spirals in mergers unlikely to be an
environmental effect and must, therefore, arise from differing time-scales of
detectability for spirals and ellipticals. We find that merging galaxies have a
wider spread in colour than the global galaxy population, with a significant
blue tail resulting from intense star formation in spiral mergers. Galaxies
classed as star-forming using their emission-line properties have average
star-formation rates approximately doubled by the merger process though star
formation is negligibly enhanced in merging elliptical galaxies. We conclude
that the internal properties of galaxies significantly affect the time-scales
over which merging systems can be detected (as suggested by recent theoretical
studies) which leads to spirals being `over-observed' in mergers. We also
suggest that the transition mass $3\times10^{10}{M}_{\astrosun}$, noted by
\citet{kauffmann1}, below which ellipticals are rare could be linked to disc
survival/destruction in mergers.
