* Astronomy

Title: The Tully-Fisher Zero Point Problem
Authors: Aaron A. Dutton (UCSC), Frank C. van den Bosch (MPIA), Stéphane Courteau (Queen's)

A long standing problem for hierarchical disk galaxy formation models has been the simultaneous matching of the zero point of the Tully-Fisher relation and the galaxy luminosity function (LF). We illustrate this problem for a typical disk galaxy and discuss three solutions: low stellar mass-to-light ratios, low initial dark halo concentrations, and no halo contraction. We speculate that halo contraction may be reversed through a combination of mass ejection through feedback and angular momentum exchange brought about by dynamical friction between baryons and dark matter during the disk formation process.

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