A shallow dark matter halo in Ultra Diffuse Galaxy AGC 242019: are UDGs structurally similar to low surface brightness galaxies?

TL;DR

This study shows that the ultra diffuse galaxy AGC 242019 has a shallow dark matter halo profile similar to low surface brightness galaxies, supporting the idea that UDGs are not a separate class but part of a continuum.

Contribution

The paper demonstrates that UDG AGC 242019 has a dark matter halo with a shallow inner slope consistent with theoretical expectations, linking UDGs to LSBs.

Findings

UDG AGC 242019's rotation curve fits a shallow dark matter profile

Structural properties of UDGs resemble those of LSBs

Internal processes like supernova feedback may shape UDG profiles

Abstract

A central question regarding Ultra Diffuse Galaxies (UDGs) is whether they are a separate category to Low Surface Brightness (LSB) galaxies, or just their natural continuation towards low stellar masses. In this letter, we show that the rotation curve of the gas rich UDG AGC 242019 is well fit by a dark matter halo with inner slope that asymptotes to -0.54, and that such fit provides a concentration parameter that matches theoretical expectations. This finding, together with previously works in which shallow inner profiles are derived for UDGs, shows that the structural properties of these galaxies are like other observed LSBs. UDGs show slowly rising rotation curves and this favours formation scenarios in which internal processes, such as SNae driven gas outflows, are acting to modify UDGs profiles.