Constraints on the mass and self-coupling of Ultra-Light Scalar Field Dark Matter using observational limits on galactic central mass

Abstract

It is well known that Ultra-Light Dark Matter (ULDM), usually scalar fields of mass m ∼ 10 −22 eV, can solve some of the outstanding problems of the Cold Dark Matter (CDM) paradigm. Such a scalar field could have non-negligible self-coupling λ. In this work, using the known observational upper limit on the amount of centrally concentrated dark matter in a galaxy, we arrive at the observational constraints in the λ − m (self coupling − mass) parameter space. It is found that the observational limit on the mass m of the ULDM depends upon the sign and strength of the self-interactions. We demonstrate that, for m ∼ 10 −22 eV, self-coupling values of O(10 −96 ) (corresponding to a scattering length of a s ∼ 10 −82 m) can be probed using limits on the dark matter mass within 10 pc of the centre of M87 galaxy. Our analysis suggests that if Ultra Light Axions (ULAs) form all of dark matter, its mass has to be less than ∼ 6 × 10 −23 eV.

Tidal disruption of solitons in self-interacting ultralight axion dark matter

“…However, see[46,47] for analytic studies and idealized simulations of ULAs with repulsive self-interactions in the Thomas-Fermi regime, and see[48] for joint constraints on the ULA mass and self-coupling from the enclosed mass profile of M87.…”