Flat Central Density Profile and Constant DM Surface Density in Galaxies from Scalar Field Dark Matter

TL;DR

This paper demonstrates that scalar field dark matter (SFDM) models can accurately fit galaxy rotation curves, naturally produce constant central surface densities, and offer a promising alternative to standard dark matter models.

Contribution

The study shows that Bose-Einstein Condensate dark matter haloes fit galaxy rotation data better than some traditional profiles and introduces a model-independent core radius definition.

Findings

SFDM fits rotation curves of low surface brightness galaxies.

SFDM predicts constant dark matter central surface density.

A new model-independent core radius definition is proposed.

Abstract

The scalar field dark matter (SFDM) model proposes that galaxies form by condensation of a scalar field (SF) very early in the universe forming Bose-Einstein Condensates (BEC) drops, i.e., in this model haloes of galaxies are gigantic drops of SF. Here big structures form like in the LCDM model, by hierarchy, thus all the predictions of the LCDM model at big scales are reproduced by SFDM. This model predicts that all galaxies must be very similar and exist for bigger redshifts than in the LCDM model. In this work we show that BEC dark matter haloes fit high-resolution rotation curves of a sample of thirteen low surface brightness galaxies. We compare our fits to those obtained using a Navarro-Frenk-White and Pseudo-Isothermal (PI) profiles and found a better agreement with the SFDM and PI profiles. The mean value of the logarithmic inner density slopes is -0.27 +/- 0.18. As a second result we find a natural way to define the core radius with the advantage of being model-independent. Using this new definition in the BEC density profile we find that the recent observation of the constant dark matter central surface density can be reproduced. We conclude that in light of the difficulties that the standard model is currently facing the SFDM model can be a worthy alternative to keep exploring further.