The stellar mass density within spiral galaxy disks

Although K-band images provide quite a reliable estimate of the stellar mass distribution within the disks of spiral galaxies, we discuss how performing a color correction to reduce local stellar mass-to-light ratio variations leads to shorter disk scale lengths and has a notable effect on the morphology. We use the mass maps prepared in this way to derive an accurate potential for the stellar mass and perform 2D hydrodynamical gas simulations to model the gas flow in a combined disk-halo potential. By comparison with the galaxy's measured kinematics, the simulated velocity fields allow us to constrain the contribution of a smooth dark matter component to the total mass in the inner few exponential disk scale lengths in spiral galaxies. We show for a sample of 3 galaxies that the simulations enable us to explore stellar disk and dark halo mass fractions.