Slowly rotating gas-rich galaxies in modified Newtonian dynamics (MOND)

TL;DR

This study tests the predictions of MOND using gas-rich dwarf galaxies with rotation curves that deviate from theoretical expectations, aiming to identify potential challenges to MOND's validity.

Contribution

The paper identifies specific gas-rich dwarf galaxies that challenge MOND predictions, highlighting the need for more precise observations to test the framework.

Findings

Holmberg II and NGC 4861 likely inconsistent with MOND

ESO 364-G029 is a promising target for testing MOND

Deeper observations could provide a strong test of MOND

Abstract

We have carried out a search for gas-rich dwarf galaxies that have lower rotation velocities in their outskirts than MOdified Newtonian Dynamics (MOND) predicts, so that the amplitude of their rotation curves cannot be fitted by arbitrarily increasing the mass-to-light ratio of the stellar component or by assuming additional undetected matter. With presently available data, the gas-rich galaxies UGC 4173, Holmberg II, ESO 245-G05, NGC 4861 and ESO 364-G029 deviate most from MOND predictions and, thereby, provide a sample of promising targets in testing the MOND framework. In the case of Holmberg II and NGC 4861, we find that their rotation curves are probably inconsistent with MOND, unless their inclinations and distances differ significantly from the nominal ones. The galaxy ESO 364-G029 is a promising target because its baryonic mass and rotation curve are similar to Holmberg II but presents a higher inclination. Deeper photometric and HI observations of ESO 364-G029, together with further decreasing systematic uncertainties, may provide a strong test to MOND.