Outer and inner mass distributions of the irregular galaxies UGC 4284 and UGC 11861: Constraining the baryonic content through stellar population synthesis studies

TL;DR

This study analyzes the mass distribution of two irregular galaxies, UGC 4284 and UGC 11861, using stellar population synthesis and rotation curves, revealing dark matter models that best fit their observed dynamics.

Contribution

It compares multiple dark matter halo models, including Einasto and Stadel, to better constrain their applicability to real galaxy rotation curves.

Findings

Cored dark matter models better fit UGC 11861 rotation curves.

DiCintio model better reproduces UGC 4284 Hα rotation curve.

Einasto and Stadel models provide superior fits among exponential models.

Abstract

In this article we investigate the outer and inner mass distributions of the irregular galaxies UGC 4284 and UGC 11861, taking advantage of published HI and H{\alpha} high resolution rotation curves and constraining the stellar disk 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 to explain the incongruity between the observed HI and H{\alpha} rotation curves of UGC 4284 and UGC 11861 and the derived baryonic rotation curves. We consider NFW, Burkert, DiCintio, Einasto, and the Stadel dark matter halos, to analyse the dark matter content of UGC 4284 and UGC 11861. The principal results of this work are that cored dark matter models better reproduce the dark matter H{\alpha} and HI rotation curves of UGC 11861 and the dark matter HI rotation curve of UGC 4284, while, the H{\alpha} rotation curve of UGC 4284 is better reproduced by a cuspy DiCintio DM model. In general, cored exponential two-parameters 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 dark matter models, Einasto and Stadel, in an attempt to better constrain the range of possible exponential dark matter models applied to real galaxies.