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 \U0001d4aa(10-96) (corresponding to a scattering length of as ∼ 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 Axion particles (ULAs) form all of dark matter, dark matter particle mass must be less than ∼ 6 × 10-23 eV.