Understanding local Dwarf Spheroidals and their scaling relations under MOND

Aims. Using a specific form of the interpolation MOND function, we explore some of the consequences for dwarf spheroidal galaxies. Methods. The particular form of the interpolation function used, leads to a law of gravity which naturally accounts for Newtonian and MONDian phenomena. We show that this does not violate dynamical constraints at sub-galactic and solar system scales, does not degrade the good fit of the MOND proposal at large galactic scales, and in fact, slightly improves the accordance with observations at dSph scales. This formalism yields a good description of gravitational phenomena without the need to invoke the presence of the still undetected and hypothetically dominant dark matter. Results. Isothermal equilibrium density profiles then yield projected surface density profiles for the local dSph galaxies in very good agreement with observational determinations, for values of the relevant parameters as inferred from recent observations of these Galactic satellites. The observed scaling relations for these systems are also naturally accounted for within the proposed scheme. Conclusions. The results obtained shed some light into the form that the MOND interpolating function may have for the most challenging regime, which occurs at moderate accelerations and intermediate mass–weighted lengths.