The Challenge of the Largest Structures in the Universe to Cosmology

摘要

Large galaxy redshift surveys have long been used to constrain cosmologicalmodels and structure formation scenarios. In particular, the largest structuresdiscovered observationally are thought to carry critical information on theamplitude of large-scale density fluctuations or homogeneity of the universe,and have often challenged the standard cosmological framework. The Sloan GreatWall (SGW) recently found in the Sloan Digital Sky Survey (SDSS) region castsdoubt on the concordance cosmological model with a cosmological constant (i.e.the flat LCDM model). Here we show that the existence of the SGW is perfectlyconsistent with the LCDM model, a result that only our very large cosmologicalN-body simulation (the Horizon Run 2, HR2) could supply. In addition, we reporton the discovery of a void complex in the SDSS much larger than the SGW, andshow that such size of the largest void is also predicted in the LCDM paradigm.Our results demonstrate that an initially homogeneous isotropic universe withprimordial Gaussian random phase density fluctuations growing in accordancewith the General Relativity, can explain the richness and size of the observedlarge-scale structures in the SDSS. Using the HR2 simulation we predict that afuture galaxy redshift survey about four times deeper or with 3 magnitudefainter limit than the SDSS should reveal a largest structure of brightgalaxies about twice as big as the SGW.