Galactic mass-to-light ratios with superfluid dark matter

Abstract

Context. We make rotation curve fits to test the superfluid dark matter model. Aims. 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). Methods. We fitted the superfluid dark matter model to the rotation curves of 169 galaxies in the SPARC sample. Results. 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. Conclusions. 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.

Approximate treatment of noncommutative curvature in quartic matrix model

“…Also, (3.9b) tells us that coupling of any external field to Φ 2 would, in principle, shift the mass parameter and, consequently, the transition lines. In a more realistic NC model, a coupling with a gravitational field of the galaxy (⇔ RΦ 2 ) could thus cause the dark matter (⇔ Φ) to behave differently in regions with strong and weak gravity (or on larger scales where the space is effectively flat), which is, as we understand, the idea behind the superfluid dark matter hypothesis [37][38][39]. If the curvature term is modified to flatten out at large distances, the change in the dark matter's behavior with scale could perhaps be realized as a decoupling of the matrix field into a direct sum of two components of different masses and in different phases.…”

From Galactic Bars to the Hubble Tension: Weighing Up the Astrophysical Evidence for Milgromian Gravity

“…This argument also applies to EG, and more generally to any theory that attempts to reproduce the RAR by simply adding an extra force to the Newtonian gravity-the extra force would need to have the deep-MOND behaviour (Equation (1)), leading to a MOND-like description with interpolating function ν = 1 + 1/ √ y. This does not agree with the observed RAR, perhaps explaining why SFDM has difficulty matching galaxy RCs with plausible M /L ratios-especially if lensing constraints are also included [365]. In addition, serious theoretical difficulties have been identified with SFDM when trying to make it covariant [366].…”

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