tokens: ACKNOWLEDGEMENTS The authors would like to thank James Willis for his help with the velociraptor halo finder, and Aaron Ludlow, Cedric Lacey, Richard Bower, Shy Genel, Greg Bryan, and Rob Crain for helpful discussions that contributed significantly to this work. They would also like to thank the anonymous reviewer, who provided many useful suggestions that helped clarify our explanations. This work was initiated as a project for the Kavli Summer Program in Astrophysics held at the Center for Computational Astrophysics of the Flatiron Institute in 2018. The program was co-funded by the Kavli Foundation and the Simons Foundation. We thank them for their generous support. This work was supported by collaborative visits funded by the Cosmology and Astroparticle Student and Postdoc Exchange Network (CASPEN). JB is supported by Science and Technology Facilities Council (STFC) studentship ST/R504725/1. DAA is supported by the Flatiron Institute, which is supported by the Simons Foundation. This work used the ARCHER UK National Supercomputing Service. This work used the DiRAC@Durham facility managed by the Institute for Computational Cosmology on behalf of the STFC DiRAC HPC Facility ( www.dirac.ac.uk ). The equipment was funded by BEIS capital funding via STFC capital grants ST/K00042X/1, ST/P002293/1, ST/R002371/1, and ST/S002502/1, Durham University, and STFC operations grant ST/R000832/1. DiRAC is part of the National e-Infrastructure. We would like to extend our thanks specifically to Alastair Basden and his team for managing the DiRAC Memory Intensive service. Software citations This paper made use of the following software packages: GIZMO (Hopkins 2017 ) gadget (Springel 2005 ) swift (Schaller et al. 2016 ) python (Rossum 1995 ), with the following libraries: numpy (Oliphant 2006 ) scipy (Jones et al. 2001 ) py-sphviewer (Benitez-Llambay 2015 ) caesar (Thompson 2018 ) yt (Turk et al. 2011 ) velociraptor (Elahi et al. 2019 ) The AHF (Gill et al. 2004 ; Knollmann Knebe 2009 ).
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