Kavli Affiliate: Mark Vogelsberger
| First 5 Authors: Vinh Tran, Xuejian Shen, Daniel Gilman, Mark Vogelsberger, Stephanie O’Neil
| Summary:
Core collapse, a process associated with self-interacting dark matter (SIDM)
models, can increase the central density of halos by orders of magnitude with
observable consequences for dwarf galaxy properties and gravitational lensing.
Resonances in the self-interaction cross section, features of hidden-sector
models with light mediators and attractive potentials, can boost the strength
of self-interactions near specific relative velocities, accelerating collapse
in halos with central velocity dispersions near the resonance. To explore this
phenomenon, we present a suite of idealized N-body simulations of isolated
halos with masses $10^7$-$10^9 rm{M_odot}$ evolved under two resonant cross
section (RCS) models with localized enhancement to the cross section on scales
$v sim 5$-$50 rm{km} rm{s^{-1}}$. We show that the change in halo
internal structure depends on how the velocity distribution of bound particles
moves across resonances in the cross section during core formation and
collapse. The interplay between the velocity distribution of bound particles
and localized features of the cross section causes deviations from self-similar
evolution, a characteristic of velocity-independent cross sections, at the
level of up to $20%$. Depending on the alignment with resonant features, halos
of different masses reach different evolutionary stages after a fixed physical
time and develop diverse density profiles and rotation curves.
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