On DDO154 and Cold Dark Matter halo profiles

Abstract

We investigate the claim by Burkert and Silk (1997) that the observed rotation curve of the dwarf irregular galaxy DDO154 cannot be reconciled with the universal CDM halo profile of Navarro, Frenk & White (1996,1997) even when allowance is made for the effect of violent gas outflow events on the structure of the galaxy. 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 without invoking Burkert & Silk's proposed spheroidal MACHO component. We are able to best reproduce the observed decline in the rotation curve by postulating additional hidden disc mass, in an amount that is compatible with disc stability requirements. In the process we improve upon the results of Navarro, Eke & Frenk (1996) on the formation of halo cores by mass loss by using actual haloes from Cold Dark Matter simulations instead of Hernquist (1990) distributions.