Tying dark matter to baryons with self-interactions.

Area of Science:

• Cosmology
• Astrophysics
• Particle Physics

Background:

• Collisionless cold dark matter (CDM) models face challenges on small scales.
• Self-interacting dark matter (SIDM) offers a potential solution through particle interactions.

Purpose of the Study:

• To derive equilibrium solutions for dark matter halo density profiles in SIDM.
• To investigate the impact of baryonic matter on SIDM halo properties.
• To compare SIDM predictions with CDM and SIDM-only simulations.

Main Methods:

• Derivation of equilibrium solutions for dark matter density profiles.
• Inclusion of gravitational potentials from both dark matter and baryons.
• Analysis of halo core sizes and densities.

Main Results:

• Self-interactions drive dark matter halos towards an isothermal state.
• Halo core sizes and shapes are linked to stellar distributions.
• SIDM halos exhibit smaller core sizes and higher core densities than predicted by SIDM-only simulations, especially in baryon-dominated galaxies.
• A Milky Way dark matter core size of ~0.3 kpc was found.

Conclusions:

• SIDM models with baryonic feedback provide a more realistic description of dark matter halos.
• The derived core properties have significant implications for indirect detection of SIDM.
• The results challenge previous expectations and CDM predictions for small-scale structures.