Testing the Dark Matter Hypothesis with Low Surface Brightness Galaxies and Other Evidence

The severity of the mass discrepancy in spiral galaxies is stronglycorrelated with the central surface brightness of the disk. Progressively lowersurface brightness galaxies have ever larger mass discrepancies. No otherparameter (luminosity, size, velocity, morphology) is so well correlated withthe magnitude of the mass deficit. The rotation curves of low surface brightness disks thus provide a uniquedata set with which to probe the dark matter distribution in galaxies. The massdiscrepancy is apparent from $R = 0$ giving a nearly direct map of the halomass distribution. The luminous mass is insignificant. Interpreting the data in terms of dark matter leads to troublesomefine-tuning problems. Different observations require contradictory amounts ofdark matter. Structure formation theories are as yet far from able to explainthe observations.Comment: Accepted for publication in the Astrophysical Journal. 49 pages AAStex + 16 figure