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Figure 14: The mass discrepancy (as in Figure 10) as a function of radius in observed spiral galaxies. The curves for individual galaxies (lines) are color-coded by their characteristic baryonic surface density (as in Figure 5). In order to be completely empirical and fully independent of any assumption such as maximum disk, stellar masses have been estimated with population synthesis models [42]. The amplitude of the mass discrepancy is initially small in high–surface-density galaxies, and grows only slowly at large radii. As the baryonic surface densities of galaxies decline, the mass discrepancy becomes more severe and appears at smaller radii. This trend confirms one of the predictions of Milgrom’s law [294]. |