Soliton Formation and the Core-Halo Mass Relation: An Eigenstate Perspective

Abstract

UltraLight Dark Matter (ULDM) is an axion-like dark matter candidate with an extremely small particle mass. ULDM halos consist of a spherically symmetric solitonic core and an NFW-like skirt. We simulate halo creation via soliton mergers and use these results to explore the core-halo mass relation. We calculate the eigenstates of the merged halos and use these to isolate the solitonic core and calculate its relative contribution to the halo mass. We compare this approach to using a fitting function to isolate the core and find a difference in masses up to 30%. We analyze three families of simulations: equal-mass mergers, unequal-mass mergers, and halos with a two-step merger history. Setting the halo mass to the initial mass in the simulation does not yield a consistent core-halo relationship. Excluding material "ejected" by the collision yields a core-halo relationship with a slope of 1/3 for simultaneous mergers and roughly 0.4 for two-step mergers. Our findings suggest there is no universal core-halo mass relationship for ULDM and shed light on the differing results for the core-halo relationship previously reported in the literature.

10 pages, 8 figures; published in PRD, updated with referee changes

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• Axion minicluster streams in the solar neighbourhood
• Scalar dark matter vortex stabilization with black holes
• Bracketing the soliton-halo relation of ultralight dark matter
• Spherical solutions of the Schrödinger-Poisson system with core-tail structure
• Single and merger soliton dynamics in scalar field dark matter with and without self-interactions
• Dark Spin-2 Field Solitons as a Source of Electromagnetic Radiation
• Post-inflationary structure formation boosted by parametric self-resonance
• Dynamical reconstruction of SPARC galactic halos within self-interacting fuzzy dark matter
• Comparison of two different integration methods for the (1+1)-Dimensional Schrödinger-Poisson Equation
• Scalar Field Dark Matter: Impact of Supernovae-driven blowouts on the soliton structure of low mass dark matter halos
• Equilibrium Core and Vortex Solutions of Bose Einstein Condensate Dark Matter around a Black Hole
• A No-Go Theorem for the Mass-Radius Relation of Solitons
• Core-halo scaling relations in self-interacting scalar field dark matter