Testing dark matter halo properties using selfsimilarity
Abstract
We use selfsimilarity in Nbody simulations of scalefree models to test for resolution dependence in the mass function and twopoint correlation functions of dark matter haloes. We use 1024^{3} particle simulations performed with ABACUS , and compare results obtained with two halo finders: friendsoffriends (FOF ), and ROCKSTAR . The FOF mass functions show a systematic deviation from selfsimilarity which is explained by resolution dependence of the FOF mass assignment previously reported in the literature. Weak evidence for convergence is observed only starting from haloes of several thousand particles, and mass functions are overestimated by at least as much as $2025{{\ \rm per\ cent}}$ for haloes of 50 particles. The mass function of the default ROCKSTAR halo catalogue (with bound virial spherical overdensity mass), on the other hand, shows good convergence of the order of 50 to 100 particles per halo, with no detectable evidence at the few percent level of any systematic dependence for larger particle number. Tests show that the mass unbinding procedure in ROCKSTAR is the key factor in obtaining this much improved resolution. Applying the same analysis to the halohalo two point correlation function, we find again strong evidence for convergence only for ROCKSTAR haloes, at separations sufficiently large so that haloes do not overlap. At these separations, we can exclude dependence on resolution at the $510{{\ \rm per\ cent}}$ level once haloes have of the order of 50 to 100 particles. At smaller separations results are not converged even at significantly larger particle number, and bigger simulations would be required to establish the resolution required for convergence.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 March 2021
 DOI:
 10.1093/mnras/staa3435
 arXiv:
 arXiv:2004.08406
 Bibcode:
 2021MNRAS.501.5064L
 Keywords:

 methods: numerical;
 largescale structure of Universe;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 Astrophysics  Astrophysics of Galaxies
 EPrint:
 10 pages, 8 figures, version to match published version, small changes (note slightly more conservative bounds on convergence)