A workshop dedicated to the Theoretical Virtual Observatory will take place at IAP on April 5-6th.
The goal is to bring together experts of the Virtual Observatory and theoreticians who would like to make results of their simulations (e.g. databases or catalogs) or numerical codes available to the worldwild astronomical community.
The length of the three-dimensional filaments observed in the fourth public data-release of the SDSS is measured by examining the local skeleton. It is defined as the 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) (Ls/ Mpc)^(-1.75±0.06) Mpc/(100Mpc)^3 for 8.2 < Ls < 16.4 Mpc, where Ls is the smoothing length in Mpc. This result, which deviates only slightly, as expected, from the trivial behavior L propto Ls^-2, is in excellent agreement with LambdaCDM cosmogony, as long as the matter density parameter remains for a flat universe in the 1 sigma range 0.25 < Omega_matter < 0.4. These measurements, which are in fact dominated by linear dynamics, are not significantly sensitive to observational biases such as redshift distortion, edge effects, incompleteness and biasing between the galaxy distribution and the dark matter distribution. Hence it is argued that the local skeleton is a rather promising and discriminating tool for the analysis of filamentary structures in three-dimensional galaxy surveys.
The 3D skeleton of the SDSS
Thierry,Sousbie, Christophe Pichon, Hélène,Courtois, Stéephane Colombi, Dmitri Novikov