Figure 21: Examples of detailed MOND rotation curve fits of the HSB and LSB galaxies of Figure 13
(NGC 6946 on the left and NGC 1560 on the right). The black line represents the Newtonian
contribution of stars and gas as determined by numerical solution of the Newtonian Poisson equation
for the observed light distribution, as per Figure 13. The blue line is the MOND fit with the
function of Eq. 52 and Eq. 53, the only free parameter being the stellar mass-to-light
ratio. In the -band, the best fit value is for NGC 6946 and for
NGC 1560. In practice, the best fit mass-to-light ratio can co-vary with the distance to the galaxy
and ; here is held fixed ( ) and the distance has been held fixed to the
best observed value (5.9 Mpc for NGC 6946 [220] and 3.45 Mpc for NGC 1560 [219]). Milgrom’s
formula provides an effective mapping between the rotation curve predicted by the observed baryons
and the observed rotation, including the bumps and wiggles.
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