Halos in a dark sky: Interactively exploring the structure of dark matter halo merger trees

This paper presents a novel application that visualizes dark matter halo merger trees and their evolution through space and time. Our application enables users to interact with individual halos within these trees in order to perform a range of visual analysis tasks, including: identifying the substructure and superstructure of the halos; observing the movement of halos across a custom range of time steps; and comparing the branching attributes of multiple trees. Central to our application is the ability to navigate the halos by interactively "jumping" from tree to tree. By clearly marking halos that have "tributaries" ? that is, that split off into multiple halos or merge with one or more halos ? we make it easy for the user to traverse the complex structure of the universe. Our application is publicly available1 online and runs at interactive rates on the browser using hardware-accelerated graphics.