Dissipative dark matter on FIRE - I. Structural and kinematic properties of dwarf galaxies

We present the first set of cosmological baryonic zoom-in simulations of galaxies including dissipative self-interacting dark matter (dSIDM). These simulations utilize the Feedback In Realistic Environments galaxy formation physics, but allow the dark matter to have dissipative self-interactions analogous to standard model forces, parametrized by the self-interaction crosssection per unit mass, (sigma/m), and the dimensionless degree of dissipation, 0 < f(diss) < 1. We survey this parameter space, including constant and velocity-dependent cross-sections, and focus on structural and kinematic properties of dwarf galaxies with M-halo similar to 10(10-11)M(circle dot) and M-* similar to 10(5-8)M(circle dot). Central density profiles (parametrized as. rho alpha r(alpha)) of simulated dwarfs become cuspy when (sigma/m)(eff) greater than or similar to 0.1 cm(2) g(-1) (and f(diss) = 0.5 as fiducial). The power-law slopes asymptote to alpha approximate to -1.5 in low-mass dwarfs independent of cross-section, which arises from a dark matter 'cooling flow'. Through comparisons with dark matter only simulations, we find the profile in this regime is insensitive to the inclusion of baryons. However, when (sigma/m)(eff) << 0.1 cm(2) g(-1), baryonic effects can produce cored density profiles comparable to non-dissipative cold dark matter (CDM) runs but at smaller radii. Simulated galaxies with (sigma/m) greater than or similar to 10 cm(2) g(-1) and the fiducial f(diss) develop significant coherent rotation of dark matter, accompanied by halo deformation, but this is unlike the well-defined thin 'dark discs' often attributed to baryon-like dSIDM. The density profiles in this high cross-section model exhibit lower normalizations given the onset of halo deformation. For our surveyed dSIDM parameters, halo masses and galaxy stellar masses do not show appreciable difference from CDM, but dark matter kinematics and halo concentrations/shapes can differ.

Automated summary

The study investigates the effects of dissipative self-interacting dark matter in cosmological simulations, exploring the parameter space. Low-mass dwarf galaxies exhibit cuspy dark matter density profiles with a power-law slope of approximately -1.5. Models with higher cross-sections show dark matter rotation and halo deformation, but do not result in baryon-like thin 'dark discs'.