The Millennium Galaxy Catalogue: Dynamically Close Pairs of Galaxies and the Global Merger Rate
Open Access
- 1 October 2005
- journal article
- Published by American Astronomical Society in The Astronomical Journal
- Vol. 130 (4) , 1516-1523
- https://doi.org/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 $L_c=(252 pm 30) imes 10^6$ $L_{odot}$ for galaxies with $-22 < M_B -5 log h < -19$ with $=0.123$ and $N_c=0.0357 pm 0.0027$, $L_c= (294 pm 31) imes 10^6 L_{odot}$ for galaxies with $-21 < M_B -5 log h < -18$, with $=0.116$. 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.Comment: 26 pages, 3 figures, AJ accepted for publicatio
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