Observing merger trees in a new light

Rhys J. J. Poulton, Aaron S. G. Robotham, Chris Power, Pascal J. Elahi

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Abstract

Merger trees harvested from cosmological N-body simulations encode the assembly histories of dark matter halos over cosmic time and are a fundamental component of semi-analytical models of galaxy formation. The ability to compare the tools used to construct merger trees, namely halo finders and tree building algorithms, in an unbiased and systematic manner is critical to assess the quality of merger trees. In this paper, we present the dendrogram, a novel method to visualise merger trees, which provides a comprehensive characterisation of a halo's assembly history-tracking subhalo orbits, halo merger events, and the general evolution of halo properties. We show the usefulness of the DENDROGRAM as a diagnostic tool of merger trees by comparing halo assembly simulation analysed with three different halo finders-VELOCIRAPTOR, AHF, and ROCKSTAR-and their associated tree builders. Based on our analysis of the resulting dendrograms, we highlight how they have been used to motivate improvements to VELOCIRAPTOR. The DENDROGRAM software is publicly available online, at: https://github.com/rhyspoulton/MergerTree-Dendrograms.

Original languageEnglish
Article number042
Number of pages14
JournalPublications of the Astronomical Society of Australia
Volume35
DOIs
Publication statusPublished - 28 Nov 2018

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