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The merger rate of galaxies in the Illustris simulation: a comparison with observations and semi-empirical models

Rodriguez-Gomez, Vicente and Genel, Shy and Vogelsberger, Mark and Sijacki, Debora and Pillepich, Annalisa and Sales, Laura V. and Torrey, Paul and Snyder, Greg and Nelson, Dylan and Springel, Volker and Ma, Chung-Pei and Hernquist, Lars (2015) The merger rate of galaxies in the Illustris simulation: a comparison with observations and semi-empirical models. Monthly Notices of the Royal Astronomical Society, 449 (1). pp. 49-64. ISSN 0035-8711. https://resolver.caltech.edu/CaltechAUTHORS:20150625-115151149

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Abstract

We have constructed merger trees for galaxies in the Illustris simulation by directly tracking the baryonic content of subhaloes. These merger trees are used to calculate the galaxy–galaxy merger rate as a function of descendant stellar mass, progenitor stellar mass ratio, and redshift. We demonstrate that the most appropriate definition for the mass ratio of a galaxy–galaxy merger consists in taking both progenitor masses at the time when the secondary progenitor reaches its maximum stellar mass. Additionally, we avoid effects from ‘orphaned’ galaxies by allowing some objects to ‘skip’ a snapshot when finding a descendant, and by only considering mergers which show a well-defined ‘infall’ moment. Adopting these definitions, we obtain well-converged predictions for the galaxy–galaxy merger rate with the following main features, which are qualitatively similar to the halo–halo merger rate except for the last one: a strong correlation with redshift that evolves as ∼(1 + z)^(2.4–2.8), a power law with respect to mass ratio, and an increasing dependence on descendant stellar mass, which steepens significantly for descendant stellar masses greater than ∼2 × 10^(11)M_⊙. These trends are consistent with observational constraints for medium-sized galaxies (M* ≳ 10^(10) M_⊙), but in tension with some recent observations of the close pair fraction for massive galaxies (M* ≳ 10^(11) M_⊙), which report a nearly constant or decreasing evolution with redshift. Finally, we provide a fitting function for the galaxy–galaxy merger rate which is accurate over a wide range of stellar masses, progenitor mass ratios, and redshifts.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1093/mnras/stv264DOIArticle
http://mnras.oxfordjournals.org/content/449/1/49PublisherArticle
http://arxiv.org/abs/1502.01339arXivDiscussion Paper
ORCID:
AuthorORCID
Rodriguez-Gomez, Vicente0000-0002-9495-0079
Genel, Shy0000-0002-3185-1540
Vogelsberger, Mark0000-0001-8593-7692
Pillepich, Annalisa0000-0003-1065-9274
Torrey, Paul0000-0002-5653-0786
Springel, Volker0000-0001-5976-4599
Hernquist, Lars0000-0001-6950-1629
Additional Information:© 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2015 February 5; received 2015 February 4; in original form 2014 December 10; first published online March 14, 2015. We are grateful to Asa Bluck, Gurtina Besla, Sarah Wellons, and Joshua Suresh for useful comments and discussions.We also thank Laura Blecha for carefully reading the manuscript. VS acknowledges support by the European Research Council through ERC-StG grant EXAGAL-308037. LH acknowledges support from NASA grant NNX12AC67G and NSF grant AST-1312095.
Funders:
Funding AgencyGrant Number
European Research Council (ERC)EXAGAL-308037
NASANNX12AC67G
NSFAST-1312095
Subject Keywords:methods: numerical; galaxies: interactions; cosmology: theory
Issue or Number:1
Record Number:CaltechAUTHORS:20150625-115151149
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150625-115151149
Official Citation:Rodriguez-Gomez, V., Genel, S., Vogelsberger, M., Sijacki, D., Pillepich, A., Sales, L. V., . . . Hernquist, L. (2015). The merger rate of galaxies in the Illustris simulation: a comparison with observations and semi-empirical models. Monthly Notices of the Royal Astronomical Society, 449(1), 49-64. doi: 10.1093/mnras/stv264
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58606
Collection:CaltechAUTHORS
Deposited By: Jason Perez
Deposited On:30 Jun 2015 19:30
Last Modified:09 Mar 2020 13:19

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