Cores of dark matter haloes correlate with stellar scalelengths

Abstract

We investigate in detail the mass distribution obtained by means of high-resolution rotation curves of 25 galaxies of different morphological types. The dark matter contribution to the circular rotation velocity is well-described by resorting to a dark component, the density of which shows an inner core, i.e. a central constant density region. We find a very strong correlation between the core radius size AC and the stellar exponential scalelength RD: RC ≃ 13 [RD/(5kpc)] 1.05kpc, and between RC and the galaxy dynamical mass at this distance, Mdyn(RC). These relationships would not be expected if the core radii were the product of an incorrect decomposition procedure, or the biased result of wrong or misunderstood observational data. The very strong correlation between the dark and luminous scalelengths found here seems to hold also for different Hubble types and opens new scenarios for the nature of the dark matter in galaxies.