The Three-dimensional Skeleton of the SDSS

Abstract

The length of the three-dimensional filaments observed in the fourth public data release of the SDSS is measured using the ``local skeleton'' method. This consists of defining a set of points where the gradient of the smoothed density field is extremal along its isocontours, with some additional constraints on local curvature to probe actual ridges in the galaxy distribution. A good fit to the mean filament length per unit volume, L, in the SDSS survey is found to be L=(52500+/-6500) (L/Mpc)-1.75+/-0.06Mpc/(100 Mpc)3 for 8.2 Mpc