Some Light on the Dark Matter vs. Modified Gravity debate from Dwarf spheroidal Scalings.

Dwarf spheroidal (dSph) galaxies are the smallest galactic systems known. Also, under standard gravity, they are the most dark matter dominated systems known in astrophysics. The local sample of dSph satellites of the Milky Way comprise some two dozen systems, ranging from a few million, down to just a few thousand solar masses in stellar content, for the recently discovered ones. High quality observations of their stellar kinematics now allow detailed inferences of their structural and dynamical properties. We perform a modeling of the gravitational equilibrium configurations for a sample of he best studied dSphs under MOND, and find that a satisfactory description is obtained, without the need to invoke the presence of dark matter or any tidal effects, for a particular interpolation function, valid at this regime. We find also that the now well established scalings of the structural properties of these systems are naturally accounted for, while they require fine tuning under the dark matter hypothesis. In particular we find a previously unrecognized scaling between the inferred mass to light ratio of a particular dSph, with the age of most recent star formation episode for the system. Again, a trait which emerges naturally under any modified gravity scheme, and which appears as an unexplained coincidence under the dark matter hypothesis. [ABSTRACT FROM AUTHOR]