Please use this identifier to cite or link to this item: http://hdl.handle.net/1959.3/207820

Title

The major and minor galaxy merger rates at z < 1.5

Author(s)

Lotz, Jennifer M.;  Jonsson, Patrik;  Cox, T. J.;  Croton, Darren;  Primach, Joel R.;  Somerville, Rachel S.;  Stewart, Kyle

Abstract

Calculating the galaxy merger rate requires both a census of galaxies identified as merger candidates, and a cosmologically-averaged 'observability' timescale T_obs(z) for identifying galaxy mergers. While many have counted galaxy mergers using a variety of techniques, T_obs(z) for these techniques have been poorly constrained. We address this problem by calibrating three merger rate estimators with a suite of hydrodynamic merger simulations and three galaxy formation models. We estimate T_obs(z) for (1) close galaxy pairs with a range of projected separations, (2) the morphology indicator G-M20, and (3) the morphology indicator asymmetry A. Then we apply these timescales to the observed merger fractions at z < 1.5 from the recent literature. When our physically-motivated timescales are adopted, the observed galaxy merger rates become largely consistent. The remaining differences between the galaxy merger rates are explained by the differences in the range of mass-ratio measured by different techniques and differing parent galaxy selection. The major merger rate per unit co-moving volume for samples selected with constant number density evolves much more strongly with redshift (~ (1+z)^(+3.0 \pm 1.1)) than samples selected with constant stellar mass or passively evolving luminosity (~ (1+z)^(+0.1 \pm 0.4)). We calculate the minor merger rate (1:4 < M_{sat}/M_{primary} <~ 1:10) by subtracting the major merger rate from close pairs from the 'total' merger rate determined by G-M20. The implied minor merger rate is ~3 times the major merger rate at z ~ 0.7, and shows little evolution with redshift.

Publication type

Journal article

Research centre

Swinburne University of Technology. Faculty of Information and Communication Technologies. Centre for Astrophysics and Supercomputing

Source

Astrophysical Journal, Vol. 742, no. 2 (Dec 2011), article no. 103

Publication year

2011

FOR Code(s)

0201 Astronomical and Space Sciences

Keyword(s)

Galaxy evolution;  Galaxy interactions;  Galaxy structure;  High-redshift galaxies

Publisher

Institute of Physics Publishing

ISSN

0004-637X

Publisher URL

http://dx.doi.org/10.1088/0004-637X/742/2/103

Copyright

Copyright © 2011 The American Astronomical Society. All rights reserved. The American Astronomical Society does not allow institutions to archive either the accepted manuscript or the published version of the article. However, you can find an earlier version of the full text here: http://arxiv.org/abs/1108.2508.

Peer reviewed