The Millennium Galaxy Catalogue: Dynamically Close Galaxy Pairs and the Global Merger Rate

R. De Propris; J. Liske; S. P. Driver; P. Allen; N. J. G. Cross

doi:10.1086/433169

paper

The Millennium Galaxy Catalogue: Dynamically Close Galaxy Pairs and the Global Merger Rate

arXiv:astro-ph/0506635 · doi:10.1086/433169

Abstract

We derive the number of dynamically close companions per galaxy ( $N_{c}$ ) and their total luminosity ( $L_{c}$ ) for galaxies in the Millennium Galaxy Catalogue: $N_{c}$ is similar to the fraction of galaxies in close pairs and is directly related to the galaxy merger rate. We find $N_{c} = 0.0174 \pm 0.0015$ and $L_{c} = (252 \pm 30) \times 1 0^{6}$ $L_{⊙}$ for galaxies with $- 22 < M_{B} - 5 lo g h < - 19$ with $< z >= 0.123$ and $N_{c} = 0.0357 \pm 0.0027$ , $L_{c} = (294 \pm 31) \times 1 0^{6} L_{⊙}$ for galaxies with $- 21 < M_{B} - 5 lo g h < - 18$ , 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 $(1 + z)^{3}$ ) 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 early-type 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.

arXiv comment26 pages, 3 figures, AJ accepted for publication

The Millennium Galaxy Catalogue: Dynamically Close Galaxy Pairs and the Global Merger Rate

Abstract

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