Rotation Curve Decomposition for Size-Mass Relations of Bulge, Disk, and Dark Halo in Spiral Galaxies

Abstract

Rotation curves of more than one hundred spiral galaxies were compiled from the literature, and deconvolved into bulge, disk, and dark halo using $\chi^2$ fitting in order to determine their scale radii and masses. Correlation analyses were obtained of the fitting parameters for galaxies that satisfied selection and accuracy criteria. Size-mass relations indicate that the sizes and masses are positively correlated among different components in such a way that the larger or more massive is the dark halo, the larger or more massive are the disk and bulge. Empirical size-mass relations were obtained for bulge, disk and dark halo by the least-squares fitting. The disk-to-halo mass ratio was found to be systematically greater by a factor of three than that predicted by cosmological simulations combined with photometry. A preliminary mass function for dark halo was obtained, which is represented by the Schechter function followed by a power law.