The Triaxial Spatial Distribution of CDM Subhalos

Kavli Institute for Cosmological Physics and Department of Astronomy and Astrophysics, The University of Chicago, Chicago, IL 60637, USA

Abstract

I review recent results on the angular distribution of substructure in CDM halos. I show that the subhalo distribution is anisotropic and generally prolate with a long axis that is closely aligned with the long axis of the total mass distribution of the host halo. I show that the correlation between the subhalo distribution and the long axis of the host halo is strong both in dissipationless and dissipational gasdynamical simulations. More massive subhalos tend to be more strongly clustered along the major axis of the host halo reflecting filamentary accretion. The anisotropy of subhalos has potential implications for the interpretation of several observations. For example, I show that while the mean projected mass fraction in substructure in the central regions of CDM halos is f_sub ≈ 0.4%, f_sub is a strong function of projection angle and is ~6 times higher for projections nearly collinear with the major axis of the host.