Galactic Mass-to-Light Ratios With Superfluid Dark Matter

TL;DR

This study tests the superfluid dark matter model against galaxy rotation curves, finding that while stellar mass-to-light ratios are generally acceptable, the model struggles to naturally reproduce MOND-like behavior and conflicts with lensing data.

Contribution

It provides a comprehensive rotation curve analysis of 169 galaxies to evaluate the superfluid dark matter model's viability and its ability to replicate observed galactic phenomena.

Findings

Mass-to-light ratios are acceptable but vary unnaturally with galaxy size.

Superfluid fits often do not resemble MOND without boundary adjustments.

Total superfluid mass conflicts with gravitational lensing constraints.

Abstract

We make rotation curve fits to test the superfluid dark matter model. In addition to verifying that the resulting fits match the rotation curve data reasonably well, we aim to evaluate how satisfactory they are with respect to two criteria, namely, how reasonable the resulting stellar mass-to-light ratios are and whether the fits end up in the regime of superfluid dark matter where the model resembles modified Newtonian dynamics (MOND). We fitted the superfluid dark matter model to the rotation curves of 169 galaxies in the SPARC sample. We found that the mass-to-light ratios obtained with superfluid dark matter are generally acceptable in terms of stellar populations. However, the best-fit mass-to-light ratios have an unnatural dependence on the size of the galaxy in that giant galaxies have systematically lower mass-to-light ratios than dwarf galaxies. A second finding is that the superfluid often fits the rotation curves best in the regime where the superfluid's force cannot resemble that of MOND without adjusting a boundary condition separately for each galaxy. In that case, we can no longer expect superfluid dark matter to reproduce the phenomenologically observed scaling relations that make MOND appealing. If, on the other hand, we consider only solutions whose force approximates MOND well, then the total mass of the superfluid is in tension with gravitational lensing data. We conclude that even the best fits with superfluid dark matter are still unsatisfactory for two reasons. First, the resulting stellar mass-to-light ratios show an unnatural trend with galaxy size. Second, the fits do not end up in the regime that automatically resembles MOND, and if we force the fits to do so, the total dark matter mass is in tension with strong lensing data.