Mass models of 15 nearby dwarf and spiral galaxies are presented .
The galaxies are selected to be homogeneous in terms of the method used to determine their distances , the sampling of their rotation curves ( RCs ) and the mass–to–light ratio ( M/L ) of their stellar contributions , which will minimize the uncertainties on the mass model results .
Those RCs are modeled using the MOdified Newtonian Dynamics ( MOND ) prescription and the observationally motivated pseudo-isothermal ( ISO ) dark matter ( DM ) halo density distribution .
For the MOND models with fixed ( M/L ) , better fits are obtained when the constant a _ { 0 } is allowed to vary , giving a mean value of ( 1.13 \pm 0.50 ) \times 10 ^ { -8 } cm s ^ { -2 } , compared to the standard value of 1.21 \times 10 ^ { -8 } cm s ^ { -2 } .
Even with a _ { 0 } as a free parameter , MOND provides acceptable fits ( reduced \chi ^ { 2 } _ { r } < 2 ) for only 60 % ( 9/15 ) of the sample .
The data suggest that galaxies with higher central surface brightnesses tend to favor higher values of the constant a _ { 0 } .
This poses a serious challenge to MOND since a _ { 0 } should be a universal constant .
For the DM models , our results confirm that the DM halo surface density of ISO models is nearly constant at \rho _ { 0 } R _ { C } \sim 120 M _ { \odot } pc ^ { -2 } .
This means that if the ( M/L ) is determined by stellar population models , ISO DM models are left with only one free parameter , the DM halo central surface density .