The Diversity of Core Halo Structure in the Fuzzy Dark Matter Model

TL;DR

This paper investigates the relationship between core and halo masses in fuzzy dark matter models, revealing significant dispersion and proposing an empirical relation with uncertainties, impacting observational constraints.

Contribution

It provides a comprehensive analysis of core-halo mass relations in FDM, introducing a new empirical formula accounting for observed dispersion and uncertainties.

Findings

Dispersion in core-halo mass relation increases with halo mass.

Proposed an empirical core-halo mass relation with uncertainty estimates.

Tidal stripping may contribute to scatter in the relation.

Abstract

In the fuzzy dark matter (FDM) model, gravitationally collapsed objects always consist of a solitonic core located within a virialised halo. Although various numerical simulations have confirmed that the collapsed structure can be described by a cored NFW like density profile, there is still disagreement about the relation between the core mass and the halo mass. To fully understand this relation, we have assembled a large sample of cored haloes based on both idealised soliton mergers and cosmological simulations with various box sizes. We find that there exists a sizeable dispersion in the core-halo mass relation that increases with halo mass, indicating that the FDM model allows cores and haloes to coexist in diverse configurations. We provide a new empirical equation for a core halo mass relation with uncertainties that can encompass all previously found relations in the dispersion, and emphasise that any observational constraints on the particle mass using a tight one-to-one core-halo mass relation should suffer from an additional uncertainty on the order of 50 % for halo masses $ \ge 10^9 (8 \times 10^{-23} eV/ (mc^2))^{3/2} M_\odot$. We suggest that tidal stripping may be one of the effects contributing to the scatter in the relation.