Effect of dark matter annihilation on gas cooling and star formation

Abstract

Context. In the current paradigm of cosmic structure formation, dark matter plays a key role on the formation and evolution of galaxies through its gravitational influence. On microscopic scales, dark matter particles are expected to annihilate amongst themselves into different products, with some fraction of the energy being transferred to the baryonic component. Aims. It is the aim of the present work to show that, in the innermost regions of dark matter halos, heating by dark matter annihilation may be comparable to the cooling rate of the gas. Methods. We use analytical models of the dark matter and gas distributions in order to estimate the heating and cooling rates, as well as the energy available from supernova explosions. Results. Depending on the model parameters and the precise nature of dark matter particles, the injected energy may be enough to balance radiative cooling in the cores of galaxy clusters. On galactic scales, it would inhibit star formation more efficiently than supernova feedback. Conclusions. Our results suggest that dark matter annihilation prevents gas cooling and star formation within at least 0.01-1 per cent of the virial radius. © ESO 2007.