The dwarf Galaxy DDO 47: Testing Cusps Hiding in Triaxial Halos

TLDR: Gentile et al. as discussed by the authors performed a harmonic decomposition of the velocity field in order to search for alleged non-circular motions needed to hide a cusp, and concluded that the dark matter halo around DDO 47 is truly cored.

Abstract: We present HI data of the dwarf galaxy DDO 47, aimed at testing the hypothesis that dark halo triaxiality might induce non-circular motions resulting in rotation curves best fitted by cored halos, even if the dark matter halo is intrinsically cuspy. We performed a harmonic decomposition of the velocity field in order to search for alleged non-circular motions needed to “hide” a cusp: in DDO 47 non-circular motions are globally at a level of 2–3 km s-1 , far from being sufficient to reconcile the observed rotation curve with the Λ CDM predictions. We conclude that the dark matter halo around DDO 47 is truly cored and that a cusp cannot be hidden by non-circular motions. More details are shown in Gentile et al. (2005).