Collision frequency between dark matter subhaloes within Milky Way-like galaxies
arXiv:2511.16464Journal publication
Approach
The study derives pair distributions in relative separation and velocity from the host-halo distribution function, then compares them with orbital integrations of subhaloes in hosts selected from cosmological N-body simulations.
Main result
For the simulated sample and adopted encounter definition, the mean violent-encounter rate is approximately 210 per Gyr, corresponding to an interval of 4.7 Myr. A violent encounter means a separation smaller than the sum of the two subhalo scale radii.
Scientific implications
Subhalo encounters provide a dynamical channel relevant to dwarf-galaxy evolution. The agreement between analytical and numerical pair distributions connects encounter statistics with the phase-space structure of the host.
Scope and limitations
The rate depends on the selected host and subhalo populations and the encounter definition. It is not a rate of observable dwarf-galaxy mergers, nor a measurement of dark-matter particle scattering.