Mass models of gas-rich void dwarf galaxies

TL;DR

This study models the mass distribution of gas-rich dwarf galaxies in the Lynx-Cancer void, comparing dark matter profiles derived from different velocity field analysis methods, and finds systematic effects influence the inferred density slopes.

Contribution

It provides the first detailed mass models of void dwarf galaxies and highlights how analysis techniques affect dark matter profile measurements.

Findings

Halo concentration parameters are similar to those in denser regions.

Average density slope from 3-D fits aligns with NFW expectations.

2-D fitting results suggest possible systematic biases.

Abstract

We construct mass models of eight gas rich dwarf galaxies that lie in the Lynx-Cancer void. From NFW fits to the dark matter halo profile, we find that the concentration parameters of halos of void dwarf galaxies are similar to those of dwarf galaxies in normal density regions. We also measure the slope of the central dark matter density profiles, obtained by converting the rotation curves derived using 3-D (\fat) and 2-D (ROTCUR) tilted ring fitting routines, into mass densities. We find that the average slope ($\alpha = -1.39 \pm 0.19$), obtained from 3-D fitting is consistent with that expected from an NFW profile. On the other hand, the average slope measured using the 2-D approach is closer to what would be expected for an isothermal profile. This suggests that systematic effects in velocity field analysis have a significant effect on the slope of the central dark matter density profiles. Given the modest number of galaxies we use for our analysis, it is important to check these results using a larger sample.