  Little is known about the content and distribution of dark matter in spiral
galaxies. To break the degeneracy in galaxy rotation curve decompositions,
which allows a wide range of dark matter halo density profiles, an independent
measure of the mass surface density of stellar disks is needed. Here, we
present our ongoing Disk Mass project, using two custom-built Integral Field
Units, to measure the vertical velocity dispersion of stars in ~40 spiral
galaxies. This will provide a kinematic measurement of the stellar disk mass
required to break the degeneracy, enabling us to determine the dark matter
properties in spiral galaxies with unprecedented accuracy. Here we present
preliminary results for three galaxies with different central disk surface
brightness levels.

Astrophysics