Velocity dispersion profiles of dwarf spheroidal galaxies with self-interacting ultralight dark matter

Dark-matter-dominated dwarf galaxies provide an excellent laboratory for testing dark matter models at small scale and, in particular, the ultralight dark matter (ULDM) class of models. Within the framework of self-interacting bosonic dark matter, we use the observed velocity-dispersion profiles of seven dwarf spheroidal galaxies to constrain the parameters of ULDM. In our modeling, we account for the impact of the baryonic component on the velocity dispersion and ULDM halo structure. We find that the repulsive self-interaction of ULDM, which fits the observations, is almost negligible, consistent with non-interacting ULDM with a boson mass of approximately $1.6\times {10}^{-22}\mathrm{e}\mathrm{V}$. In contrast, for attractively interacting ULDM, the best fit corresponds to a smaller boson mass of about $1.3\times {10}^{-22}\mathrm{e}\mathrm{V}$, with self-interaction playing a significant role in shaping the dark-matter halo and thereby influencing the interpretation of observations.