Do Halos that Form Early, Have High Concentration, Are Part of a Pair, or Contain a Central Galaxy Potential Host More Pronounced Planes of Satellite Galaxies?

Abstract

Abstract The Milky Way, the Andromeda galaxy, and Centaurus A host flattened distributions of satellite galaxies that exhibit coherent velocity trends indicative of rotation. Comparably extreme satellite structures are very rare in cosmological ΛCDM simulations, giving rise to the “satellite plane problem.” As a possible explanation, it has been suggested that earlier-forming, higher-concentration host halos contain more flattened and kinematically coherent satellite planes. We have tested for such a proposed correlation between the satellite plane and host halo properties in the Exploring the Local Volume in Simulations suite of simulations. We find evidence for neither a correlation of plane flattening with halo concentration or formation time nor a correlation of kinematic coherence with concentration. The height of the thinnest subhalo planes does correlate with the host virial radius and the radial extent of the subhalo system. This can be understood as an effect of not accounting for differences in the radial distribution of subhalos and selecting them from different volumes than covered by the actual observations. Being part of a halo pair like the Local Group does not result in narrower or more correlated satellite planes either. Additionally, using the Phat ELVIS simulations, we show that the presence of a central galaxy potential does not favor narrower or more correlated satellite planes; rather, it leads to slightly wider planes. Such a central potential is a good approximation of the dominant effect baryonic physics in cosmological simulations has on a subhalo population. This suggests that, in contrast to other small-scale problems, the issue of planes of satellite galaxies is made worse by accounting for baryonic effects.