http://arxiv.org/abs/2110.00259
Recently, work on self-interacting dark matter (SIDM) cosmologies has shown that an enormous diversity of dark matter (DM) halo density profiles is possible for a fixed SIDM model, ranging from the development of low-density cores to high-density core-collapsed cusps. The possibility of the growth of high central density in low-mass halos, accelerated if halos are subhalos of larger systems, has intriguing consequences for small-halo searches with substructure lensing. However, following the evolution of $\lesssim 10^8 M_\odot$ subhalos in lens-mass systems ($\sim 10^{13}M_\odot$) is computationally expensive with traditional N-body simulations. In this work, we develop a new hybrid semi-analytical + N-body method to study the evolution of SIDM subhalos with high fidelity, from core formation to core-collapse, in staged simulations. With this method, we are able to capture the evaporation of subhalo particles by interactions with host halo particles, an effect that has not yet been fully explored in the context of subhalo core-collapse. We find three main processes driving subhalo evolution: subhalo internal heat outflow, host-subhalo evaporation, and tidal effects. We conclude that the subhalo central density grows only when the heat outflow outweighs the energy gain from evaporation and tidal heating. Thus, evaporation delays or even disrupts subhalo core-collapse. We map out the parameter space for subhalos to core-collapse, and find that it is nearly impossible to drive core collapse in subhalos in SIDM models with constant cross sections. Any discovery of ultra-compact dark substructures with future substructure lensing observations disfavors SIDM models with constant cross sections, indicating instead the presence of additional degrees of freedom, such as velocity-dependence or dissipation of energy.
Z. Zeng, A. Peter, X. Du, et. al.
Mon, 4 Oct 21
1/76
Comments: 24 pages, 14 figures, 2 animations