On DDO 154 and cold dark matter halo profiles

We investigate the claim by Burkert & Silk that the observed rotation curve of the dwarf irregular galaxy DDO 154 cannot be reconciled with the,univer sal CDM halo profile of Navarro, Frenk & White, even when allowance is made for the effect of violent gas outflow events on the structure of the galax y. By means of N-body simulations we show that under certain conditions it is possible to obtain a reasonable fit to the observed rotation curve witho ut invoking Burkert & Silk's proposed spheroidal MACHO component. We are ab le to reproduce the observed decline in the rotation curve best by postulat ing additional hidden disc mass, in an amount that is compatible with disc stability requirements. In the process we improve upon the results of Navar ro, Eke & Frenk on the formation of halo cores by mass-loss by using actual haloes from cold dark matter simulations instead of Hernquist distribution s.