The rotation curves of low surface brightness ( LSB ) galaxies suggest that they possess significantly higher mass-to-light ( M / L ) ratios than their high surface brightness counterparts , indicating that LSB galaxies may be dark matter dominated .
This interpretation is hampered by the difficulty of disentangling the disc and dark halo contributions from the disc dynamics of LSB galaxies .
Recently , Fuchs ( 2002 ) has attempted such a disentanglement using spiral arm density wave and swing amplification theory , allowing an independent measurement of the disc mass ; this work suggests that LSB discs are significantly more massive than previously believed .
This would considerably reduce the amount of matter required in the dark halos in fitting the rotation curves .
Interestingly , the high mass-to-light ratios derived for the discs appear inconsistent with standard stellar population synthesis models .

In this paper , we investigate whether the high M / L ratios for the Fuchs LSB discs might be understood by adopting a very “ bottom heavy ” initial mass function ( IMF ) .
We find that an IMF with a power law exponent of around \alpha = 3.85 
( compared to the standard Salpeter IMF , \alpha = 2.35 ) is sufficient to explain the unusually high M / L ratios of the Fuchs sample .
Within the context of the models , the blue colours ( ( B - R ) _ { 0 } < 1.0 ) of the sample galaxies result from being metal-poor ( [ Fe/H ] = -1.5 \sim - 1.0 ) and having undergone recent ( \sim 1 - 3 Gyr ago ) star formation .