Fuzzy dark matter halos with repulsive self-interactions: coherent soliton and halo vortex network with moderate self-coupling (2507.00293v1)

Abstract: We examine the impact of repulsive self-interactions of moderate strength on fuzzy dark matter halos focusing on the core and granule size, the spatial dependence of the field's coherence, the turbulent vortex tangle and the oscillation frequency of the central soliton. Our analysis extends across the range from quantum-pressure-dominated to self-interaction-dominated stabilisation of the gravitationally bound solitonic core. Within this examined range of self-coupling strengths, we find that mergers with a given initial spatial configuration and an increasing self-interaction strength $g$, result in cores with increased size that exhibit a reduced central density and oscillate with decreased frequency. All of these features are in accordance with expectations from the study of isolated Self-interacting Fuzzy Dark Matter (SFDM) solitons. The characteristic size of the granules in the surrounding halo also grows but by a much smaller amount relative to the core; accordingly, typical inter-vortex distances are also only mildly affected. We also measure the total length of the vortex network which, although less robust, shows no clear dependence on increasing $g$ and no signs of decay over the timescales of our simulations. Measures of coherence of the field behave as in the non-interacting case, again clearly separating the coherent core form the quasi-coherent halo. Interestingly, we observe a relative increase of incoherent fluctuations coexisting with the coherent mode at the centre of the halo with increasing self-coupling strength, a phenomenon also observed in laboratory condensates at non-zero temperature.