The impact of the dark matter-gas interaction on the collapse behavior of spherical symmetric systems

Abstract

Context. If the gas in the evolving cosmic halos is dissipating energy (cooling), then the dark matter (DM) halo also undergoes a compactification because of the variation in the gravitational potential . This is well-known as adiabatic contraction (AC).Aims. Complementary to the AC, we investigate the resulting dynamical behavior of the whole system if the backreaction of the AC of DM onto the gas is taken into account.Methods. Also to achieve sufficient high resolution within the central halo region, we use a crude fluid approximation for the DM obeying the adiabatic contraction behavior. Furthermore, we restrict ourselves to spherical symmetry and vanishing angular momentum of the studied matter configurations. The computations are done using a first-order Godunov scheme.Results. Our results show that the dynamical interaction between gas and DM may lead to significantly shorter collapse times. If the gas cools, the dynamical behavior of the whole system depends strongly on the shape of the initial density profile. Conclusions. Our findings indicate that, for a certain mass range of halo configurations, the dynamical interaction between gas and DM might be important for the halo evolution so it must be taken into account. © 2008 ESO.