MEASURING THE COSMIC WEB

Leibniz-Institut fur¨ Astrophysik Potsdam (AIP), An der Sternwarte 16, D-14482 Potsdam, Germany; vmueller@aip.de; hoffmann@ice.cat; snuza@aip.deReceived: 2011 July 10; accepted: 2011 August 1Abstract. A quantitative study of the clustering properties of the cosmicweb as a function of absolute magnitude and color is presented using the SDSSData Release 7 galaxy survey. Mark correlations are included in the analysis.We compare our results with mock galaxy samples obtained with four differentsemi-analytical models of galaxy formation imposed on the merger trees of theMillenium simulation. The clustering of both red and blue galaxies is studiedseparately.Key words: cosmology: observations – cosmology: theory – galaxies: statis-tics – large scale structure of the Universe1. INTRODUCTIONThe 200 years history of the Tartu Observatory is strongly linked with theexploration of the Earth and space at different scales. In the early 19th century,the triangulation along the Tartu Meridian Arc, 3000 km across Europe, helped todetermine the size and precise shape of the Earth. First stellar parallax measure-ments (besides Bessel) by Wilhelm Struve, the founder of the Tartu Observatory,provided the basis for exploring our neighborhood within the Milky Way. Thedynamical distance measurements of the Andromeda nebula and other island uni-verses by Ernst Opik¨ in 1918–1922 opened the way to the first systematic worksin the field of extragalactic astronomy.The study of the large scale distribution of galaxies became an important re-search subject already over 50 years ago with the notion of filamentary structure asrevealed by the Lick galaxy survey (Shane & Wirtanen 1954). The impression of acellular structure of the Universe with dominance of filaments and large voids in thegalaxy distribution was developed during the period 1974-1980 at the cosmologyschool of Tartu Observatory (Joeveer, Einasto & Tago 1978; Einasto, Joeveer &Saar 1980). These results were presented at the IAU Symposium No. 79 at Tallinn(Longair & Einasto 1978) where an exposition of the pancake theory of large scalestructure formation was presented by Zel’dovich, Doroshkevich, Shandarin, Sigovand Kotok (see e.g. Zel’dovich 1978). Already at this time, galaxy formation inproto-clusters was discussed by Doroshkevich, Saar & Shandarin (1978).A quantitative description of the galaxy clustering was provided for the first