2015MNRAS.451..353R

In this paper, we investigate the outer and inner mass distributions of the irregular galaxies UGC 4284 and UGC 11861, taking advantage of published Hi and Hα high-resolution rotation curves and constraining the stellar disc of both galaxies throughout stellar population synthesis studies. In addition, we take into account the gas content of both galaxies deriving the Hi+He rotation curve. The deduced baryonic rotation curves (star+gas) are inadequate to account for the total mass of UGC 4284 and UGC 11861, for that reason we examine the possibility of dark matter (DM) to explain the incongruity between the observed Hi and Hα rotation curves of UGC 4284 and UGC 11861 and the derived baryonic rotation curves. We consider NFW, Burkert, DiCintio, Einasto, and the Stadel DM haloes, to analyse the DM content of UGC 4284 and UGC 11861. The principal results of this work are that cored DM models better reproduce the DM Hα and Hi rotation curves of UGC 11861 and the DM Hi rotation curve of UGC 4284, while the Hα rotation curve of UGC 4284 is better reproduced by a cuspy DiCintio DM model. In general, cored exponential two-parameter models Einasto and Stadel give better fits than Burkert. This trend, as well as to confirm past results, presents for the first time a comparison between two different exponential DM models, Einasto and Stadel, in an attempt to better constrain the range of possible exponential DM models applied to real galaxies.