The universal rotation curve of spiral galaxies — I. The dark matter connection

Abstract We use a homogeneous sample of about 1100 optical and radio rotation curves (RCs) and relative surface photometry to investigate the main mass structure properties of spirals, over a range of 6 mag and out to ≾ 1.5 and 2 optical radii (for the optical and radio data, respectively). We confirm the strong dependence on luminosity for both the profile and the amplitude of RCs claimed by Persic (ii) the central halo density scales as L−0.7; (iii) the halo core radius is comparable to the optical radius, but shrinks for low luminosities; (iv) the total halo mass scales as L0.5. Such scaling properties can be represented as a curve in the (luminosity)-(DM/LM mass ratio)-(DM core radius)-(DM central density) space, which provides a geometrical description of the tight coupling between the dark and the luminous matter in spiral galaxies.