A Natural Explanation of the VPOS from Multistate Scalar Field Dark Matter

TL;DR

This paper proposes that the multistate scalar field dark matter model naturally explains the observed anisotropic distribution of satellite galaxies, known as the VPOS, by accounting for quantum states and temperature effects in galactic halos.

Contribution

It introduces a multistate scalar field dark matter model that explains the VPOS phenomenon through quantum states and early universe temperature corrections.

Findings

The model fits rotation curves of multiple galaxies.

It explains the anisotropic satellite distribution (VPOS).

Different galaxies' properties depend on the final temperature of the scalar field.

Abstract

Observations with the Gaia satellite have confirmed that the satellite galaxies of the Milky Way are not distributed as homogeneously as expected. The same occurs in galaxies such as Andromeda and Centaurus A, where satellites around their host galaxies have been observed to have orbits aligned perpendicular to the galactic plane of the host galaxy. This problem is known for the Milky Way as Vast Polar Structure (VPOS). The Scalar Field Dark Matter Field (SFDM), also known as Ultralight-, Fuzzy-, BEC-, and Axion-dark matter, proposes dark matter is a scalar field, which in the non-relativistic limit follows the Schr\"odinger equation coupled to the Poisson equation. Although the SF here is classical, the Schr\"odinger equation contains a ground and excited states as part of its nature. In this work, we show that such quantum character of the SFDM can naturally explain the VPOS observed in galaxies. By taking into account the finite temperature corrections for a complex, self-interacting SF at very early epochs of the Universe, we show that with the ground and first excited states in the Newtonian limit, we can fit the rotation curves of the host galaxies. With the best-fit parameters obtained, we can explain the VPOS. We do this with particular galaxies, such as the Milky Way, Andromeda, Centaurus A, and 6 other galaxies whose satellites have been observed. This result shows that the multistate SFDM is not distributed homogeneously around the galaxy, and therefore might explain the anisotropic distribution of the satellite galaxies. According to this result, this could be a general characteristic of the galaxies in the Universe. Finally, we also show how the scale of each galaxy depends on a parameter determined by the final temperature of the SF galactic halo under study. This might explain why different galaxies with SFDM give different values of the mass of the SF.