Tidal dwarf galaxies as a test of fundamental physics

TL;DR

This paper tests the validity of Newtonian dynamics versus MOND in explaining the rotation curves of tidal dwarf galaxies, finding MOND provides a better fit without additional dark matter assumptions.

Contribution

It demonstrates that MOND can naturally explain TDG rotation curves, challenging the need for dark matter in these systems within the current cosmological framework.

Findings

MOND fits TDG rotation curves without extra dark matter.

Newtonian dynamics require additional dark matter or specific viewing angles.

Results are robust across different inclination assumptions.

Abstract

Within the cold dark matter (CDM) framework tidal dwarf galaxies (TDGs) cannot contain dark matter, so the recent results by Bournaud et al. (2007) that 3 rotating TDGs do show significant evidence for being dark matter dominated is inconsistent with the current concordance cosmological theory unless yet another dark matter component is postulated. We confirm that the TDG rotation curves are consistent with Newtonian dynamics only if either an additional dark matter component is postulated, or if all 3 TDGs happen to be viewed nearly edge-on, which is unlikely given the geometry of the tidal debris. We also find that the observed rotation curves are very naturally explained without any free parameters within the modified Newtonian dynamics (MOND) framework if inclinations are adopted as derived by Bournaud et al. We explore different inclination angles and two different assumptions about the external field effect. The results do not change significantly, and we conclude therefore that Newtonian dynamics has severe problems while MOND does exceedingly well in explaining the observed rotation curves of the 3 TDGs studied by Bournaud et al.