The Caterpillar Project: A Large Suite of Milky Way Sized Halos

Abstract

We present the largest number of Milky Way sized dark matter halos simulated at very high mass ($\sim$\ $10^4$ \Msol/particle) and temporal resolution (5 Myrs/snapshot) done to date, quadrupling what is currently available in the literature. This initial suite consists of the first 24 halos of the whose project goal of 60 – 70 halos will be made public when complete. We do not bias our halo selection by the size of the Lagrangian volume. We resolve $\sim$20,000 gravitationally bound subhalos within the virial radius of each host halo. Improvements were made upon current state-of-the-art halo finders to better identify substructure at such high resolutions, and on average we recover $\sim$4 subhalos in each host halo above 10$^8$\ \Msol which would have otherwise not been found. The density profiles of relaxed host halos are reasonably fit by Einasto profiles ($\alpha$ = 0.169 $\pm$ 0.023) with dependence on the assembly history of a given halo. Averaging over all halos, the substructure mass fraction is $f_{m,subs} = 0.121 \pm 0.041$, and mass function slope is d$N$/d$M\propto M^{-1.88 \pm 0.10}$. We find concentration-dependent scatter in the normalizations at fixed halo mass. Our detailed contamination study of 264 low-resolution halos has resulted in unprecedentedly large high-resolution regions around our host halos for our fiducial resolution (sphere of radius $\sim1.4 \pm 0.4$ Mpc). This suite will allow detailed studies of low mass dwarf galaxies out to large galactocentric radii and the very first stellar systems at high redshift ($z$ $\geq$ 15).

Publication
The Astrophysical Journal, Volume 818, Issue 1, 10, 19 pp. (2016).
Brendan Griffen
CTO & co-founder

Working at the intersection of computer science, engineering and biology.