Speaker
Description
Halo density profiles in CDM follow a fixed functional form (e.g., NFW) that predicts over-dense cuspy inner regions compared with observed cores. Alternative DM models like Scalar Field (Fuzzy) Dark Matter (SFDM) aim to tackle this by producing cores balanced by quantum pressure and gravity. However, strong structure formation constraints on SFDM have motivated the need for Self-Interactions (SI). In this talk I address whether SI can alleviate these tensions in SFDM.
We demonstrate that repulsive quartic SI produces solitonic cores embedded in NFW envelopes, reproducing both 1D rotation curves and explicit dynamical reconstruction of host halos in 3D via the Gross-Pitaevskii-Poisson equations for 17 DM-dominated galaxies in the SPARC dataset using a single boson mass (m) and interaction strength (g) pair. This analysis is then extended to the LITTLE THINGS dataset.
The core radius is a function of (m, g) which gives rise to a localised microphysical parameter degeneracy. We resolve this using Hierarchical Gibbs Sampling, thus placing early benchmarks on repulsive quartic SI in SFDM against competing DM models through Bayesian Model Comparison.
We generalise the analysis by extending across a family of ground-state potentials in SFDM - non-interacting, quartic SI, quartic+sextic SI, the full cosine SI, and the logarithmic SI – to systematically map most of the ground-state SFDM landscape. This framework is shifted to the Ultra Faint Dwarf regime to significantly suppress baryonic feedback effects on DM constraints. This is motivated by astrophysical tensions with observed constant central surface density ($\rho_c r_c =$ constant) and its slope mismatch with theory predictions. We comment on the validity of this test and how the analysis either constrains which SFDM potential survives, or, if the relation does not hold fundamentally, delivers benchmark scaling relations across the SFDM family.