Does the galaxy NGC1052-DF2 falsify Milgromian dynamics?

TL;DR

This paper investigates whether the ultra-diffuse galaxy NGC1052-DF2 challenges Milgromian dynamics (MOND) by considering external gravitational effects, concluding that it remains consistent with MOND when these effects are included.

Contribution

The study demonstrates that accounting for external gravitational fields resolves the apparent conflict between NGC1052-DF2 observations and MOND predictions.

Findings

NGC1052-DF2's dynamics are consistent with MOND when external fields are included.

External gravitational effects are crucial for accurate MOND predictions.

The galaxy does not falsify MOND as previously claimed.

Abstract

A great challenge in present-day physics is to understand whether the observed internal dynamics of galaxies is due to dark matter matter or due to a modification of the law of gravity. Recently, van Dokkum et al. reported that the ultra-diffuse dwarf galaxy NGC1052-DF2 lacks dark matter, and they claimed that this would -- paradoxically -- be problematic for modified gravity theories like Milgromian dynamics (MOND). However, NGC1052-DF2 is not isolated, so that a valid prediction of its internal dynamics in MOND cannot be made without properly accounting for the external gravitational fields from neighbouring galaxies. Including this external field effect following Haghi et al. shows that NGC1052-DF2 is consistent with MOND.