Core-halo scaling relations in self-interacting scalar field dark matter

TL;DR

This study investigates how self-interactions in scalar field dark matter influence halo structures, revealing that interaction type and strength significantly affect core properties and evolution, with implications for astrophysics.

Contribution

The paper provides the first comprehensive simulation-based analysis of self-interacting scalar field dark matter halos, extending core-halo relations beyond free fuzzy dark matter.

Findings

Repulsive interactions produce more massive, extended cores with lower densities.

Attractive interactions increase core densities and can lead to collapse.

Scaling relations depend on interaction strength, sign, and halo evolution stage.

Abstract

We study the impact of self-interactions on the structure and evolution of scalar field dark matter (SFDM) halos. Using three-dimensional Gross-Pitaevskii-Poisson simulations of multiple soliton mergers, we explore both repulsive and attractive regimes across a wide range of scattering lengths. Our results show that repulsive self-interactions lead to more massive and extended cores with lower central densities compared to the free (non-interacting) fuzzy dark matter case, while attractive interactions enhance central densities and can drive cores toward collapse, once a critical mass is exceeded. We confirm that the mass-radius relation of solitonic cores is well described by analytical predictions, even in the presence of self-interactions, and we extend the core-halo mass relation to scenarios beyond fuzzy dark matter. We find that the scaling relations between core mass, size, and total energy are not universal but depend sensitively on the strength and sign of the self-interaction, as well as on the evolutionary stage of the halo. These results demonstrate that self-interactions provide a natural mechanism to regulate core properties, with important implications for the formation of supermassive black holes and for potential astrophysical signatures in galactic cores.