The Millennium Galaxy Catalogue: Dynamically close pairs of galaxies and the global merger rate

  • Roberto De Propris, H. H. Wills, Jochen Liske
  • Published 2005

Abstract

We derive the number of dynamically close companions per galaxy (Nc) and their total luminosity (Lc) for galaxies in the Millennium Galaxy Catalogue: Nc is similar to the fraction of galaxies in close pairs and is directly related to the galaxy merger rate. We find Nc = 0.0174±0.0015 and Lc = (252±30)×10 6 L⊙ for galaxies with −22 < MB − 5 log h < −19 with < z >= 0.123 and Nc = 0.0357± 0.0027, Lc = (294± 31)× 10 6 L⊙ for galaxies with −21 < MB − 5 log h < −18, with < z >= 0.116. The integrated merger rate to z = 1 for both samples is about 20 %, but this depends sensitively on the fraction of kinematic pairs that are truly undergoing a merger (assumed here to be 50%), the evolution of the merger rate (here as (1 + z)) and the adopted timescale for mergers (0.2 and 0.5 Gyr for each sample, respectively). Galaxies involved in mergers tend to be marginally bluer than non-interacting galaxies and show an excess of both earlytype and very late-type objects and a deficiency of intermediate-type spirals. This suggests that interactions and mergers partly drive the star formation and morphological evolution of galaxies. Subject headings: galaxies: interactions

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Cite this paper

@inproceedings{Propris2005TheMG, title={The Millennium Galaxy Catalogue: Dynamically close pairs of galaxies and the global merger rate}, author={Roberto De Propris and H. H. Wills and Jochen Liske}, year={2005} }