Scalar Field Wave (Fuzzy) Dark Matter and the Formation of Galaxies

Abstract

We investigate Scalar Field Wave Dark Matter in the context of galactic Dark Matter halos. In particular, we offer an analysis of the Baryonic Tully-Fisher Relation (BTFR). We detail a particular family of excited state solutions to the Einstein-Klein-Gordon equations, and use it to provide a novel theoretical model for producing the BTFR. We then solve this model computationally to simulate the BTFR. Interpreting the Dark Matter scalar field as an ultralight boson, this returns a conservative mass constraint of $m\geq 10^{-23}eV$. Assuming slightly stronger conditions suggests $m\geq 10^{-22}eV$ to be more compatible with the BTFR. We provide a discussion of Scalar Field Dark Matter rotation curves and the structure of Scalar Field Dark Matter halos. Compatibility with the BTFR requires the excited state solutions to obey particular boundary conditions; this may have implications for the behavior of Dark Matter halos and the formation of galaxies.