Speaker
Description
Conventionally, halos are considered subhalos if their center lies within the radius of their hosts. However, definitions of the halo boundary vary throughout the literature, such that some halos are not consistently labeled as standalone structures or subhalos. What structures are considered discrete impacts quantities critical to our halo models, such as the halo mass or correlation function. To resolve this issue, we will discuss a new proposed definition for subhalos grounded in dynamics: a halo is a subhalo if and only if it has had a pericenter around a larger halo. We apply this definition to an N-body simulation and compare the halo mass function, subhalo-to-halo mass ratios, and subhalo radial distributions between our proposed and conventional definitions. We also employ particle-tracking techniques to examine how this definition changes the mass and spatial distributions of the subhalos lost by conventional halo finders. Furthermore, we show that the proposed definition removes artifacts like "backsplash" halos from these important quantities, demonstrating the strengths of defining subhalos in this way.
