Unstable Cold Dark Matter and the Cuspy Halo Problem in Dwarf Galaxies

Abstract

We speculate that the dark halos of dwarf galaxies and low surface brightness galaxies soften their central cusps by the decay of a fraction of cold dark matter (CDM) particles to a stable particle with a recoiling velocity of a few tens km s$^{-1}$, after they have driven the formation of galactic halos. This process, however, does not necessarily produce a significant reduction of the central dark matter density of satellite dwarf spheroidals like Draco or Fornax. It is shown that the recovered distribution of concentration parameters $c$ for the initial (before decay) Navarro-Frenk-White halos, is in good agreement with CDM predictions. Other interesting potentials of unstable CDM are highlighted.