SDSS DR7 superclusters

The catalogues^⋆

¹ Tartu Observatory, 61602 Tõravere, Estonia
e-mail: juhan.liivamagi@ut.ee
² Institute of Physics, University of Tartu, Tähe 4, 51010 Tartu, Estonia
³ National Institute of Chemical Physics and Biophysics, Rävala 10, 10143 Tallinn, Estonia
⁴ Estonian Academy of Sciences, Kohtu 6, 10130 Tallinn, Estonia

Received: 9 December 2010
Accepted: 22 November 2011

Abstract

We have constructed a set of supercluster catalogues for the galaxies from the SDSS survey main and luminous red galaxy (LRG) flux-limited samples. To delineate superclusters, we calculated luminosity density fields using the B₃-spline kernel of the radius of 8 h^-1 Mpc for the main sample and 16 h^-1 Mpc for the LRG sample and define regions with densities over a selected threshold as superclusters, while utilising almost the whole volume of both samples. We created two types of catalogues, one with an adaptive local threshold and a set of catalogues with different global thresholds. We describe the supercluster catalogues and their general properties. Using smoothed bootstrap, we find uncertainty estimates for the density field and use these to attribute confidence levels to the catalogue objects. We have also created a test catalogue for the galaxies from the Millennium simulation to compare the simulated and observed superclusters and to clarify the methods we use. We find that the superclusters are well-defined systems, and the properties of the superclusters of the main and LRG samples are similar. We also show that with adaptive local thresholds we get a sample of superclusters, the properties of which do not depend on their distance from the observer. The Millennium galaxy catalogue superclusters are similar to those observed.