2016ApJ...832...88B

We present theoretical constraints for the formation of the newly discovered dark star clusters (DSCs) with high mass-to-light (\mathcalM/\mathcalL) ratios, from Taylor et al. These compact stellar systems photometrically resemble globular clusters (GCs) but have dynamical \mathcalM/\mathcalL ratios of ∼10-100, closer to the expectations for dwarf galaxies. The baryonic properties of the DSCs suggest that their host dark matter halos likely virialized at high redshift with \mathcalM>10⁸M_☉. We use a new set of high-resolution N-body simulations of Centaurus A to determine whether there is a set of z = 0 subhalos whose properties are in line with these observations. While we find such a set of subhalos, when we extrapolate the dark matter density profiles into the inner 20 pc, no dark matter halo associated with Centaurus A in our simulations, at any redshift, can replicate the extremely high central mass densities of the DSCs. Among the most likely options for explaining 10⁵-10⁷M_☉ within subhalos of 10 pc diameter is the presence of a central massive black hole (BH). We therefore propose that the DSCs are remnant cusps of stellar systems surrounding the central BHs of dwarf galaxies that have been almost completely destroyed by interactions with Centaurus A.