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The evolution of assembly bias

Contreras, S; Zehavi, I; Padilla, N; Baugh, CM; Jiménez, E; Lacerna, I

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S Contreras

I Zehavi

N Padilla

E Jiménez

I Lacerna


We examine the evolution of assembly bias using a semi-analytical model of galaxy formation implemented in the Millennium-WMAP7 N-body simulation. We consider fixed number density galaxy samples ranked by stellar mass or star formation rate. We investigate how the clustering of haloes and their galaxy content depend on halo formation time and concentration, and how these relationships evolve with redshift. At z = 0 the dependences of halo clustering on halo concentration and formation time are similar. At higher redshift, halo assembly bias weakens for haloes selected by age, and reverses and increases for haloes selected by concentration, consistent with previous studies. The variation of the halo occupation with concentration and formation time is also similar at z = 0 and changes at higher redshifts. Here, the occupancy variation with halo age stays mostly constant with redshift but decreases for concentration. Finally, we look at the evolution of assembly bias reflected in the galaxy distribution by examining the galaxy correlation functions relative to those of shuffled galaxy samples that remove the occupancy variation. This correlation functions ratio monotonically decreases with larger redshift and for lower number density samples, going below unity in some cases, leading to reduced galaxy clustering. While the halo occupation functions themselves vary, the assembly bias trends are similar whether selecting galaxies by stellar mass or star formation rate. Our results provide further insight into the origin and evolution of assembly bias. Our extensive occupation function measurements and fits are publicly available and can be used to create realistic mock catalogues.


Contreras, S., Zehavi, I., Padilla, N., Baugh, C., Jiménez, E., & Lacerna, I. (2019). The evolution of assembly bias. Monthly Notices of the Royal Astronomical Society, 484(1), 1133-1148.

Journal Article Type Article
Acceptance Date Jan 1, 2019
Online Publication Date Jan 9, 2019
Publication Date Mar 31, 2019
Deposit Date Apr 11, 2019
Publicly Available Date Apr 11, 2019
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 484
Issue 1
Pages 1133-1148


Published Journal Article (5.2 Mb)

Copyright Statement
© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.

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