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Title: Major Mergers Going Notts: Challenges for Modern Halo Finders
Authors: Behroozi, P.
Knebe, A.
Pearce, F. R.
Elahi, P.
Han, J.
Lux, H.
Mao, Y-Y.
Muldrew, Stuart Iain
Potter, D.
Srisawat, C.
First Published: 2015
Citation: Monthly Notices of the Royal Astronomical Society, 2015 (Accepted)
Abstract: Merging haloes with similar masses (i.e., major mergers) pose significant challenges for halo finders. We compare five halo finding algorithms' (AHF, HBT, Rockstar, SubFind, and VELOCIraptor) recovery of halo properties for both isolated and cosmological major mergers. We find that halo positions and velocities are often robust, but mass biases exist for every technique. The algorithms also show strong disagreement in the prevalence and duration of major mergers, especially at high redshifts (z>1). This raises significant uncertainties for theoretical models that require major mergers for, e.g., galaxy morphology changes, size changes, or black hole growth, as well as for finding Bullet Cluster analogues. All finders not using temporal information also show host halo and subhalo relationship swaps over successive timesteps, requiring careful merger tree construction to avoid problematic mass accretion histories. We suggest that future algorithms should combine phase-space and temporal information to avoid the issues presented.
ISSN: 0035-8711
eISSN: 1365-2966
Version: Post-print
Status: Peer-reviewed
Type: Journal Article
Rights: Copyright © 2015, the authors. This is a pre-copyedited, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The version of record MNRAS, 2015 (In print) is available online at: Deposited with reference to the publisher’s open access archiving policy, available at
Appears in Collections:Published Articles, Dept. of Physics and Astronomy

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