Isolated and non-isolated dwarfs in terms of modified Newtonian dynamics

TL;DR

This study tests modified Newtonian dynamics (MOND) on two dwarf galaxies in different environments, confirming MOND's consistency with observed kinematics and refining the understanding of their rotation curves.

Contribution

First mass model of KK 246's rotation curve within MOND and a revised, more accurate rotation curve for Holmberg II based on HI data.

Findings

KK 246's kinematics align with MOND predictions.

Holmberg II's rotation velocity is higher than previously thought, consistent with MOND.

Revised inclination angle for Holmberg II improves model fit.

Abstract

Within the framework of modified Newtonian dynamics (MOND) we investigate the kinematics of two dwarf spiral galaxies belonging to very different environments, namely KK 246 in the Local Void and Holmberg II in the M81 group. A mass model of the rotation curve of KK 246 is presented for the first time, and we show that its observed kinematics are consistent with MOND. We re-derive the outer rotation curve of Holmberg II, by modelling its HI data cube, and find that its inclination should be closer to face-on than previously derived. This implies that Holmberg II has a higher rotation velocity in its outer parts, which, although not very precisely constrained, is consistent with the MOND prediction.