Internal kinematics of dwarf galaxies orbitally moving in ultralight dark matter

Abstract

For dwarf galaxies modeled as deformed Plummer spheres and orbitally moving in ultralight dark matter halo of the Milky Way, the torque induced by the dynamical friction force is determined and obtained to be much smaller than the torque produced by the gravitational force of the Milky Way. As to the tidal torque, it is found that its magnitude differs significantly for the Plummer and Gaussian density profiles of ultralight dark matter. Possible oscillations of dwarf galaxies caused by the tidal torque and misalignment of dwarf galaxies with respect to their equilibrium position are investigated. It is suggested that more accurate measurements of dwarf-galaxy rotation velocities and improved modeling of dark matter distributions could provide useful constraints on the nature and properties of dark matter.