The Baryonic Tully-Fisher Relation and Dark Matter in Nearby Spirals

The baryonic Tully‐Fisher relation (BTF) and its implications for dark matter in spiral galaxies are reviewed in the context of next‐generation neutral hydrogen (HI) instruments and surveys. Spanning 5 decades in disk mass, the BTF is among the tightest known galaxy scaling relations. Recent work by McGaugh [1,2] suggests that the scatter in the BTF is minimal for a specific choice of disk mass‐to‐light ratio Υ*. Mass models of nearby spirals with these Υ* imply halo concentrations that are systematically lower than predicted by collisionless simulations of halo assembly. HI observations of statistically complete galaxy samples in cosmologically relevant volumes will be required to elucidate the origin of both the BTF and corresponding constraints on the dark matter distributions in disk galaxies.