|
Description
The Lambda-cold dark matter (Lambda CDM) scenario is able to describe the Universe at large scales, but clearly shows some serious difficulties at small scales. The core/cusp issue is one of those: as a fact, the inner dark matter (DM) density profiles of spiral galaxies generally appear to be cored, without the r^-1^ profile as predicted by N-body simulations in the above scenario. It is well known that, in a more physical context, the baryons in the galaxy, through supernovae explosions could back react and erase the original cusp. Before investigating the efficiency and the presence of such effect, it is important to know how wide and how frequent the discrepancy between observed and N-body predicted profiles is and what its features are. We use more than 3200 good quality and high resolution, quite extended rotation curves (RCs) of disk systems including normal and dwarf spirals as well as low surface brightness galaxies covering their whole ranges of magnitudes. All these RCs are condensed in 26 coadded RCs, each of them built with individual RCs of galaxies of similar luminosity and morphology. We mass model these 26 RCs using the NFW profile for the contribution of the DM halo to the circular velocity and the exponential Freeman disk for that of the stellar disk. The fits are generally poor in all the 26 cases: in several cases we find chi^2^_red_> 2. Moreover, the best fitting values of three parameters of the model (c, M_D_, M_{vir}_) combined with those of their 1-sigma uncertainty show clear conflict with well-known expectations of Lambda-CDM scenario. We also test the scaling relations which exist in spirals with the outcome of the current mass modelling: the latter is found not to account for such scaling relations. The results of testing NFW profile in disk systems indicate that such DM halo density law cannot account for the kinematics of the whole family of disk galaxies. The need of transforming initial cusps in the observed cores is therefore mandatory for the success of the Lambda-CDM scenario, in any disk galaxy of any luminosity or maximum rotational velocity.
|
