Low-surface-brightness spheroidal galaxies as Milgromian isothermal spheres.

I consider a sample of eight pressure-supported low-surface brightness galaxies (seven nearby dwarfs and one ultra-diffuse object) in terms of Milgrom's modified Newtonian dynamics (MOND). These objects are modelled as Milgromian isotropic isothermal spheres characterised by two parameters that are constrained by observations: the constant line-of-sight velocity dispersion and the central surface density. The velocity dispersion determines the total mass, and, with the implied mass-to-light ratio, the central surface brightness. This then specifies the radial run of surface brightness over the entire isothermal sphere. For the objects in this sample the predicted radial distribution of surface brightness is shown to be entirely consistent with observations which constitutes a success for MOND that is independent of the reduced dynamical mass.