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Galaxy Zoo: the properties of merging galaxies in the nearby Universe - local environments, colours, masses, star formation rates and AGN activity

Research output: Contribution to journalArticlepeer-review

  • Daniel W. Darg
  • Sugata Kaviraj
  • Chris J. Lintott
  • Kevin Schawinski
  • Marc Sarzi
  • Steven P. Bamford
  • Joseph Silk
  • Dan Andreescu
  • Professor Bob Nichol
  • M. Jordan Raddick
  • Anze Slosar
  • Alexander S. Szalay
  • Professor Daniel Thomas
  • Jan Vandenberg
Following the study of Darg et al., we explore the environments, optical colours, stellar masses, star formation and active galactic nucleus activity in a sample of 3003 pairs of merging galaxies drawn from the Sloan Digital Sky Survey using visual classifications from the Galaxy Zoo project. While Darg et al. 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 × 1010 M⊙, noted by Kauffmann et al., below which ellipticals are rare could be linked to disc survival/destruction in mergers.
Original languageEnglish
Pages (from-to)1552-1563
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date21 Jan 2010
Publication statusPublished - 2010


  • MNRAS-2010-Darg-1552-63

    Rights statement: Copyright 2009 The Authors. Journal compilation Copyright 2009 RAS

    Final published version, 1.22 MB, PDF document

    Licence: CC BY-SA

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