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Unformatted text preview: In the most extreme cases, the rotation curve is flat to almost 100 kpc. Clearly, most of the mass is in a more extended distribution than stars or gas - the "missing mass" (even though what is missing is in our brains, not in the mass). There are trends of the mass distribution with Hubble type, as mapped by Rubin et al 1985 ApJ 289, 81: the form of the rotation curve is fairly constant, with the amplitude changing from Sa to Sc. The maximum rotation velocity has median values 299,222,175 km/s for Sa, Sb, and Sc, respectively. In all cases, the correlation with luminosity dominates for individual galaxies. It is traditional to trace some aspects of the mass distribution via the mass-to-light ratio M/L in solar units, running from a few for young stellar assemblies to several hundred for galaxy halos and clusters. Not only does this reduce the big galaxy-small galaxy bias, but it is also distance-independent for traditional dynamical mass estimates....
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