Core-Envelope Haloes in Scalar Field Dark Matter with Repulsive Self-Interaction: Fluid Dynamics Beyond the de Broglie Wavelength

Understand

Scalar Field Dark Matter (SFDM) comprised of ultralight bosons has attracted great interest as an alternative to standard, collisionless Cold Dark Matter (CDM) because of its novel structure-formation dynamics, described by the coupled Schr\"odinger-Poisson equations.

• In the free-field ("fuzzy") limit of SFDM (FDM), structure is inhibited below the de Broglie wavelength, but resembles CDM on larger scales.
• Virialized haloes have "solitonic" cores of radius $\sim\lambda_\text{deB}$, surrounded by CDM-like envelopes.
• When a strong enough repulsive self-interaction (SI) is also present, structure can be inhibited below a second length scale, $\lambda_\text{SI}$, with $\lambda_\text{SI}> \lambda_\text{deB}$ -- called the Thomas-Fermi (TF) regime.