Halo Parameters of Spiral Galaxies

Extract

We have made a rotation curve analysis of a sample of spiral galaxies for which both photometric and kinematical data of reasonable quality are available in the literature. From the photometric radial luminosity profile, assuming constant mass-to-light ratios for bulge and disk separately, we calculate a rotation curve due to the luminous mass in a galaxy. Comparison with the observed rotation velocities allows us to derive a halo rotation curve, which can be used to derive characteristic halo parameters. The decomposition into luminous and dark matter is not unique, with as extremes a “minimum” disk (M/L = 0) and a “maximum” disk (M/L as high as possible while requiring a realistic halo mass distribution without a hollow core).