On the mass of ultra-light bosonic dark matter from galactic dynamics

TL;DR

This paper investigates the mass range of ultra-light scalar particles as dark matter candidates by analyzing galactic dynamics, especially dwarf spheroidal galaxies, using simulations and observational constraints.

Contribution

It establishes a preferred mass range for ultra-light bosonic dark matter particles based on galactic dynamics and simulations, considering both non-interacting and self-interacting scenarios.

Findings

Mass range 0.3x10^-22 eV to 1x10^-22 eV fits galactic observations

Scalar field halos can explain longevity of cold clumps and globular cluster distributions

Results align with cosmic microwave background and substructure suppression constraints

Abstract

We consider the hypothesis that galactic dark matter is composed of ultra-light scalar particles and use internal properties of dwarf spheroidal galaxies to establish a preferred range for the mass m of these bosonic particles. We re-investigate the problem of the longevity of the cold clump in Ursa Minor and the problem of the rapid orbital decay of the globular clusters in Fornax and dwarf ellipticals. Treating the scalar field halo as a rigid background gravitational potential and using N-body simulations, we have explored how the dissolution timescale of the cold clump in Ursa Minor depends on m. It is demonstrated that for masses in the range 0.3x10^-22 eV < m <1x10^-22 eV, scalar field dark halos without self-interaction would have cores large enough to explain the longevity of the cold clump in Ursa Minor and the wide distribution of globular clusters in Fornax, but small enough to make the mass of the dark halos compatible with dynamical limits. It is encouraging to see that this interval of m is consistent with that needed to suppress the overproduction of substructure in galactic halos and is compatible with the acoustic peaks of cosmic microwave radiation. On the other hand, for self-interacting scalar fields with coupling constant l, values of m^4/l <= 0.55x10^3 eV^4 are required to account for the properties of the dark halos of these dwarf spheroidal galaxies.