The Topology of the 2-Degree Field Galaxy Redshift Survey

Abstract

We analyse the topology of density surfaces drawn from the recently completed southern galactic strip (SGP) of the 2-degree field galaxy redshift survey (2dFGRS). We calculate the genus curves of the smoothed density fields drawn from the 2dFGRS SGP on scales ranging from 5 h⁻¹ Mpc to 50 h⁻¹ Mpc and compare them with the genus curves of the density fields with the same power spectrum but random phases, therefore measuring the level of phase correlation present in 2dF. We find that on scales larger than 15 h⁻¹ Mpc the measured genus curves of 2dF are very close to those expected for gaussian random fields. Below this scale, however, we can observe non-gaussianity which we believe originates from non-linear gravitational evolution. The unprecedented number of resolution elements in 2dF allows us to measure non- gaussianity with great accuracy.