The universal rotation curve of dwarf disk galaxies

TL;DR

This study demonstrates that dwarf disk galaxies exhibit a universal rotation curve similar to larger spirals, dominated by dark matter with core sizes between 2-3 disc lengths, revealing tight structural correlations.

Contribution

We extend the universal rotation curve concept to dwarf galaxies, showing their dark matter halos have consistent core sizes and densities, and introduce a new parameter for light distribution compactness.

Findings

Dwarf galaxies follow a universal rotation curve similar to larger spirals.

Dark matter dominates these systems with a core radius of 2-3 stellar disc lengths.

Structural properties of dark and luminous matter are strongly correlated.

Abstract

We use the concept of the spiral rotation curves universality to investigate the luminous and dark matter properties of the dwarf disc galaxies in the local volume (size $\sim11$ Mpc). Our sample includes 36 objects with rotation curves carefully selected from the literature. We find that, despite the large variations of our sample in luminosities ($\sim$ 2 of dex), the rotation curves in specifically normalized units, look all alike and lead to the lower-mass version of the universal rotation curve of spiral galaxies found in Persic et al. We mass model the double normalized universal rotation curve $V(R/R_{opt})/V_{opt}$ of dwarf disc galaxies: the results show that these systems are totally dominated by dark matter whose density shows a core size between 2 and 3 stellar disc scale lengths. Similar to galaxies of different Hubble types and luminosities, the core radius $r_0$ and the central density $\rho_0$ of the dark matter halo of these objects are related by $ \rho_0 r_0 \sim 100\hspace{0.1cm} \mathrm{M_\odot pc^{-2}}$. The structural properties of the dark and luminous matter emerge very well correlated. In addition, to describe these relations, we need to introduce a new parameter, measuring the compactness of light distribution of a (dwarf) disc galaxy. These structural properties also indicate that there is no evidence of abrupt decline at the faint end of the baryonic to halo mass relation. Finally, we find that the distributions of the stellar disc and its dark matter halo are closely related.