Properties of globular clusters formed in dark matter mini-halos

Abstract

We seek to differentiate dynamical and morphological attributes between globular clusters (GCs) that were formed inside their own dark matter (DM) mini-halo from those who were not. We employed high-resolution full N-body simulations on a Graphics Processing Unit (GPU) of the GCs with and without a DM mini-halo, orbiting a Fornax-like dwarf galaxy. For GCs with DM, we observed that this dark extra mass triggers a tidal radius growth that allows the mini-halo to act as a protective shield against tidal stripping, being itself stripped beforehand. We demonstrate that this shielding effect becomes negligible when the tidal radius is smaller than the half-mass radius of the mini-halo. Contrary to previous predictions, we found that the inflation of outer stellar velocity dispersion profiles is expected for GCs with and without a mini-halo, as a result of the host’s tidal field. Moreover, we observed that GCs with a DM mini-halo should have, in general, relatively more radial outer velocity anisotropy profiles throughout all of their orbits, smaller degrees of internal rotation, and as a consequence of the latter, smaller ellipticities for their stellar distribution. Due to dynamical friction, we observed a clear bimodal evolutionary distribution of GCs with and without DM in the integrals of motion space and show that for GCs originally embedded in DM, this method is not reliable for association with previous accretion events. Finally, we provide parametric mass profiles of disrupted DM mini-halos from GCs that are to be used in Jeans modelling and orbital integration studies.