Description
The fundamental physical properties of Dark Matter (DM) e.g. particle
mass, spin, couplings, etc. still remain a mystery. If DM particles are spinless and
ultralight ($m \sim 10^{-22}\ \text{eV}$), what are the observational implications of
properties like mass and in particular, self-couplings? We attempt to answer this
question by considering the following astrophysical scenarios: (a) requiring that
observed galactic rotation curves of dwarf galaxies as well as an empirical
soliton-halo relation have to be simultaneously satisfied allows one to probe
self-couplings as small as $\lambda \sim \mathcal{O}(10^{-90})$, and (b) survival
of dwarf satellite galaxies orbiting in the potential of larger halos on cosmological
timescales can be used to probe both attractive and repulsive self-couplings as
small as $\lambda \sim \pm 10^{-92}$.
