MOND Rotation Curve Fits

The most stringent test of any hypothesized force law is whether, given the observed distribution of mass, it predicts the correct motions.

This page lists the tally of galaxies whose dynamical data are and are not well fit by MOND. Two stringent requirements must be met for a galaxy to make this page: 1) adequate kinematic and photometric data must exist, and 2) somebody must have bothered to do the MOND analysis.

Current tally:

84-0-11
a record any coach would envy.

Galaxies well fit by MOND

84 listed at present

UGC 2885 NGC 5533 NGC 6674 NGC 7331
NGC 5907 NGC 2998 NGC 801 NGC 5371
NGC 5033 NGC 2903 NGC 3521 NGC 2683
NGC 3198 NGC 6946 NGC 2403 NGC 6503
NGC 1003 NGC 247 NGC 7739 NGC 300
NGC 5585 NGC 55 NGC 1560 NGC 3109
UGC 128 UGC 2259 M 33 IC 2574
DDO 170 DDO 168 NGC 3726 NGC 3769
NGC 3877 NGC 3893 NGC 3917 NGC 3949
NGC 3953 NGC 3972 NGC 3992 NGC 4010
NGC 4013 NGC 4051 NGC 4085 NGC 4088
NGC 4100 NGC 4138 NGC 4157 NGC 4183
NGC 4217 NGC 4389 UGC 6399 UGC 6446
UGC 6667 UGC 6818 UGC 6917 UGC 6923
UGC 6930 UGC 6973 UGC 6983 UGC 7089
NGC 1024 NGC 3593 NGC 4698 NGC 5879
IC 724 F563-1 F563-V2 F568-1
F568-3 F568-V1 F571-V1 F574-1
F583-1 F583-4 UGC 1230 UGC 5005
UGC 5999 Carina Fornax Leo I
Leo II Sculptor Sextans Sgr

Galaxies which are NOT fit by MOND

















Galaxies for which MOND fit is dubious

Galaxyproblem
NGC 2841 distance discrepant from Hubble flow value
NGC 2915 distance uncertain
DDO 154 last few points dropping (no Newtonian fit, either)
IC 1613 very uncertain inclination and asymmetric drift
F565-V2 inclination very uncertain
UGC 5750 inclination very uncertain
UGC 6446 distance uncertain
UGC 6818 interaction?
UGC 6973 very dusty - does light trace mass?
Ursa Minor very sensitive to Milky Way parameters
Draco sensitive to Milky Way parameters

Each of these cases is afflicted by substantial systematic uncertainties. Having the inclination right is very important in a MOND analysis since it enters through sin4i. Similarly, the physical scale a0 of MOND requires a proper distance to be known, which may not always be close enough to the Hubble flow value. A particularly interesting case is the dwarf Spheroidal galaxy Ursa Minor. It is very close to the Milky Way which complicates the analysis. The stellar mass-to-light ratio is unacceptably high (~17) if the standard IAU value of the Milky Way rotation velocity (220 km/s) is used. However, the analysis is very sensitive to this. If instead we adopt the more modern estimate of 185 km/s, then the mass-to-light ratio is a much more plausible 4.

Acceptable fits to all these galaxies can be found; the question is whether these are reasonably within the bounds of the uncertainties. Given the nature of astronomical data, I think this is about the right rate of goofs. (You know an astronomer is fudging when there are no goofy data points.)

I find it remarkable that in no case is the fit way off. This is usually what happens when you make up the wrong force law.