Low-surface-density galaxies and the modified dynamics

Very-low-surface-density galactic systems have very low mean accelerations. They thus provide quintessential tests of the Modified Dynamics (MOND), which predicts an increasing mass discrepancy with decreasing acceleration. We describe succinctly the results pertinent to several classes of such objects: Low-luminosity (dwarf) spirals, irregular dwarf spirals, normal-lumonosity-but -low-surface-density spirals, and dwarf-spheroidal satellites of the Milky Way.