Tully-Fisher relation, galactic rotation curves and dissipative mirror dark matter

Abstract

If dark matter is dissipative then the distributionof dark matter within galactic halos can be governed by dissipation, heating and hydrostatic equilibrium.Previous work has shown that a specific model, in the framework of mirror dark matter, can explain several empirical galactic scaling relations. It is shown here that this dynamical halo model implies a quasi-isothermal dark matter density,ρ(r) ≃ ρ0r02/(r2+r02), wherethe core radius, r0, scales with disk scale length, rD, viar0/kpc ≈ 1.4(rD/kpc). Additionally, the product ρ0r0 is roughlyconstant, i.e. independent of galaxy size(the constant is set by the parameters of the model).The derived dark matter density profile implies that the galactic rotation velocity satisfies the Tully-Fisher relation,LB∝v3max, where vmax is the maximal rotational velocity.Examples of rotation curves resulting from this dynamics are given.