On the analysis of 900 optical rotation curves: the universal rotation curve as a power law and the development of a theory-independent dark-matter modeller

Abstract

The 900 ORCs of Mathewson, Ford & Buchhorn which were folded by Persic & Salucci (astro-ph/9502091) are analysed. A technique for removing that part of an ORC most dominated by the central region it introduced (see astro-ph/0107300 for a far more comprehensive discussion of this). The analysis then shows that a power-law model of the form V = A R^b, where the parameters (A,b) differ between ORCs, provides an extremely good description of the generic behaviour of ORCs when these central regions are removed. It is shown that a very powerful correlation exists between the free parameters (A,b), and that parameter A can be very accurately modelled in terms of the luminosity properties of galaxies. The net conclusion is that the power-law model is, at the very least, an extremely good first-order model for the behaviour of disc dynamics in the outer regions of ORCs.