Radial Distributions of Dwarf Satellite Systems in the Local Volume
  The radial spatial distribution of low-mass satellites around a Milky Way
(MW)-like host is an important benchmark for simulations of small-scale
structure. The distribution is sensitive to the disruption of subhalos by the
central disk and can indicate whether the disruption observed in simulations of
MW analogs is artificial (i.e., numeric) or physical in origin. We consider a
sample of 12 well-surveyed satellite systems of MW-like hosts in the Local
Volume that are complete to $M_V<-9$ and within 150 projected kpc. We
investigate the radial distribution of satellites and compare with $\Lambda$CDM
cosmological simulations, including big-box cosmological simulations and high
resolution zoom in simulations of MW sized halos. We find that the observed
satellites are significantly more centrally concentrated than the simulated
systems. Several of the observed hosts, including the MW, are $\sim2\sigma$
outliers relative to the simulated hosts in being too concentrated, while none
of the observed hosts are less centrally concentrated than the simulations.
This result is robust to different ways of measuring the radial concentration.
We find that this discrepancy is more significant for bright, $M_V<-12$
satellites, suggestive that this is not the result of observational
incompleteness. We argue that the discrepancy is possibly due to artificial
disruption in the simulations, but, if so, this has important ramifications for
what stellar to halo mass relation is allowed in the low-mass regime by the
observed abundance of satellites.
