Figure 22: The rotation curve [124] and MOND fit [384] of the Local Group spiral M33 assuming
a constant stellar mass-to-light ratio (top panel). While the overall shape is a good match, there
is a slight mismatch at 3 kpc and above 7 kpc. The observed color gradient implies a slight
variation in the mass-to-light ratio, in the sense that the stars at small radii are slightly redder
and heavier than those at large radii. Applying stellar population models [42] to the observed color
gradient produces a slight adjustment of the Newtonian mass model. The dotted line in the lower
panel reiterates the constant model from the top panel, while the solid line has been corrected
for the observed color gradient. This slight adjustment to the baryonic mass distribution considerably
improves the fit.
|