Editor's Summary

1 October 2009

Lightening the darkness

All galaxies are thought to be surrounded by a halo of invisible 'dark matter', detectable only through its gravitational interactions. Gentile et al. report the discovery of a surprising relationship between the distributions of dark and luminous matter in galaxies spanning a wide range of observational properties. They find that within one dark halo scale-length, the mean luminous surface density is constant for galaxies of virtually all shapes and sizes. This follows the recent discovery that the mean dark matter surface density within one dark halo scale-length (the radius for which the volume density profile of dark matter remains 'flat') is virtually constant for all galaxies.

Letter: Universality of galactic surface densities within one dark halo scale-length

Gianfranco Gentile, Benoit Famaey, HongSheng Zhao & Paolo Salucci

doi:10.1038/nature08437

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