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Statistics of galaxy mergers: bridging the gap between theory and observation

Huško, Filip; Lacey, Cedric G; Baugh, Carlton M

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Authors

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Filip Husko filip.husko@durham.ac.uk
PGR Student Doctor of Philosophy



Abstract

We present a study of galaxy mergers up to z = 10 using the Planck Millennium cosmological dark matter simulation and the GALFORM semi-analytical model of galaxy formation. Utilizing the full 800 Mpc3 volume of the simulation, we studied the statistics of galaxy mergers in terms of merger rates and close pair fractions. We predict that merger rates begin to drop rapidly for high-mass galaxies (M* > 1011.3–1010.5 M⊙ for z = 0–4), as a result of the exponential decline in the galaxy stellar mass function. The predicted merger rates for massive galaxies (M* > 1010 M⊙) increase and then turn over with increasing redshift, by z = 3.5, in disagreement with hydrodynamical simulations and semi-empirical models. In agreement with most other models and observations, we find that close pair fractions flatten or turn over at some redshift (dependent on the mass selection). We conduct an extensive comparison of close pair fractions, and highlight inconsistencies among models, but also between different observations. We provide a fitting formula for the major merger time-scale for close galaxy pairs, in which the slope of the stellar mass dependence is redshift dependent. This is in disagreement with previous theoretical results that implied a constant slope. Instead, we find a weak redshift dependence only for massive galaxies (M* > 1010 M⊙): in this case the merger time-scale varies approximately as M−0.55∗⁠. We find that close pair fractions and merger time-scales depend on the maximum projected separation as r1.32max⁠, in agreement with observations of small-scale clustering of galaxies.

Citation

Huško, F., Lacey, C. G., & Baugh, C. M. (2021). Statistics of galaxy mergers: bridging the gap between theory and observation. Monthly Notices of the Royal Astronomical Society, 509(4), 5918-5937. https://doi.org/10.1093/mnras/stab3324

Journal Article Type Article
Acceptance Date Nov 15, 2021
Online Publication Date Nov 23, 2021
Publication Date 2021-02
Deposit Date May 23, 2022
Publicly Available Date Mar 29, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Electronic ISSN 1365-2966
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 509
Issue 4
Pages 5918-5937
DOI https://doi.org/10.1093/mnras/stab3324

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Copyright Statement
This article has been accepted for publication in Monthly notices of the Royal Astronomical Society. ©: 2021 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.





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