Distribution of Dark Matter in Bulge, Disk and Halo inferred from High-accuracy Rotation Curves

Abstract

High-accuracy rotation curves of spiral galaxies show a steep rise in the central few hundred pc region, indicating high concentration of mass toward the center. Using the rotation curves, we idrectly calculate radial distributions of the surface-mass density (SMD), and obtain radial profiles of the mass-to-luminosity ratio (M/L). The M/L ratio is found to vary significantly not only in the massive halo but also within the bulge and disk regions. It increases with the radius within the disk, and rapidly toward halo. In some galaxies, the M/L increases inward toward the center within the bulge, indicating a massive dark core. On these bases, we discuss the radial distribution of dark matter in spiral galaxies.