The hierarchical structure of galactic haloes: generalized N-dimensional clustering with C LUSTAR-ND

Abstract

We present C LUSTAR-ND, a fast hierarchical galaxy/(sub)halo finder that produces Clustering Structure via Transformative Aggregation and Rejection in N-Dimensions. It is designed to improve upon H ALO-OPTICS - an algorithm that automatically detects and extracts significant astrophysical clusters from the 3D spatial positions of simulation particles - by decreasing run-times, possessing the capability for metric adaptivity, and being readily applicable to data with any number of features. We directly compare these algorithms and find that not only does C LUSTAR-ND produce a similarly robust clustering structure, it does so in a run-time that is at least 3 orders of magnitude faster. In optimizing C LUSTAR-ND's clustering performance, we have also carefully calibrated 4 of the 7 C LUSTAR-ND parameters which - unless specified by the user - will be automatically and optimally chosen based on the input data. We conclude that C LUSTAR-ND is a robust astrophysical clustering algorithm that can be leveraged to find stellar satellite groups on large synthetic or observational data sets.