Is There Evidence for Flat Cores in the Halos of Dwarf Galaxies? The Case of NGC 3109 and NGC 6822

Two well studied dwarf galaxies -- NGC 3109 and NGC 6822 -- present some ofthe strongest observational support for a flat core at the center of galacticdark matter (DM) halos. We use detailed cosmologically motivated numericalmodels to investigate the systematics and the accuracy of recovering parametersof the galaxies. Some of our models match the observed structure of the twogalaxies remarkably well. Our analysis shows that the rotation curves of thesetwo galaxies are instead quite compatible with their DM halos having steepcuspy density profiles. The rotation curves in our models are measured usingstandard observational techniques. The models reproduce the rotation curves ofboth galaxies, the disk surface brightness profiles as well as the profile ofisophotal ellipticity and position angle. The models are centrally dominated bybaryons; however, the dark matter component is globally dominant. The simulateddisk mass is marginally consistent with a stellar mass-to-light ratio inagreement with the observed colors. We show that non-circular motions combinedwith gas pressure support and projection effects results in a largeunderestimation of the circular velocity in the central $\sim 1$ kpc region,creating the illusion of a constant density core. Although the systematiceffects mentioned above are stronger in barred systems, they are also presentin axisymetric disks. Our results strongly suggest that there is nocontradiction between the observed rotation curves in dwarf galaxies and thecuspy central dark matter density profiles predicted by Cold Dark Mattermodels.