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

TL;DR

This study decomposes rotation curves of over a hundred spiral galaxies into bulge, disk, and dark halo components, revealing size-mass correlations and discrepancies with cosmological predictions.

Contribution

It provides empirical size-mass relations for galaxy components and compares observed mass ratios with theoretical models.

Findings

Dark halo sizes and masses positively correlate with bulge and disk.

Disk-to-halo mass ratio exceeds cosmological predictions by a factor of three.

Dark halo mass function follows Schechter and power-law distributions.

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.