MOND and the dynamics of NGC 628
  Aniyan et al. (2018) have recently published direct measurements of the
baryonic mass distribution and the rotation curve of the almost-face-on disc
galaxy NGC 628. While its very low inclination makes this galaxy anything but
ideal for rotation-curve analysis, these new results, taken at face value, have
interesting ramifications for MOND. The methods employed afford a direct
determination of the stellar mass in the disc, which, in turn, affords a
parameter-free MOND prediction of the rotation curve, which I show. In
comparison, the dark-matter fits that Aniyan et al. present have two free
parameters. To boot, these results further negate an earlier claim deleterious
to MOND. It is that stellar $M/L$ ratios deduced from vertical velocity
dispersions in disc galaxies are rather lower than what is required by MOND
fits to rotation curves. Specifically, it was claimed that even
high-surface-density discs are, by and large, sub maximal; viz., that they show
substantial mass discrepancies near their center. This is contrary to the
prediction of MOND that in such high-acceleration regions only small
discrepancies should appear, if any to speak of. Such claims of low $M/L$
values have been rebutted before, and the fallacy that may have led to them
pointed out. The new results strongly buttress these rebuttals.
