Self Interacting Fuzzy Dark Matter and its Observational Implications

Abstract

We investigate aspects of Fuzzy Dark Matter (FDM) in both the non-interacting and repul sively self-interacting regimes, critically discussing the role of interactions on virialised profiles, using our findings to fit to galactic rotation curves of a range of dark matter dominated galax ies, thus proposing a way to numerically reconstruct a galaxy from analysing observational curves. Specifically, we firstly analyse the ground state solution of the Gross-Pitaevskii-Poisson equations- the soliton core. A generalised ansatz is formed along with a soliton-specific di mensionless interaction strength. The virial theorem is utilised to explain core dependencies on boson (m) and total mass, and self-interaction (g), and a degeneracy in the pairing of m and g is also uncovered. Moreover, we introduce a Super-Gaussian profile from empirically fitting to numerically generated self-interacting soliton ground states. This profile, joined with a Navarro-Frenk-White (NFW) halo profile, is used to fit self-interacting FDM to observational data of dark matter dominated galaxies, finding the crucial result that a single m and g pair fits all selected galaxies. Thirdly, we present three dimensional (3D) simulation results of self interacting FDM, and we demonstrate a scheme which allows us to reconstruct density profiles whose inferred rotation curves replicate observational data. In particular, we present a sim ulated self-interacting FDM halo corresponding to a galaxy for which we have observational data, specifically galaxy UGCA444. We find an elegant form of the core-halo mass relation, depending on the total energy of the system and qualitatively comment on the variation in granule number and size depending on total energy. Next, we analyse the dynamical aspects of the halo. In particular we (i) investigate the effects of m and g on the oscillation frequency of soliton cores; (ii) reveal evidence for a cooling (condensation) process, where the core density grows on time scales longer than the age of the universe; (iii) finally, we undertake a preliminary investigation of the orbital dynamics of test particles in our recreated galaxy, commenting on the velocity dispersion and the implications for the age gradient of stars in disc galaxies.