Topology of non-linear structure in the 2dF Galaxy Redshift Survey

J. Berian James, Matthew Colless, Geraint F. Lewis, John A. Peacock

Research output: Contribution to journalArticlepeer-review


We study the evolution of non-linear structure as a function of scale in samples from the 2dF Galaxy Redshift Survey, constituting over 221000 galaxies at a median redshift of z = 0.11. The two flux-limited galaxy samples, located near the Southern Galactic Pole and the Galactic equator, are smoothed with Gaussian filters of width ranging from 5 to 8h-1Mpc to produce a continuous galaxy density field. The topological genus statistic is used to measure the relative abundance of overdense clusters to void regions at each scale; these results are compared with the predictions of the analytic theory, in the form of the genus statistic for (i) the linear regime case of a Gaussian random field and (ii) a first-order perturbative expansion of the weakly non-linear evolved field. The measurements demonstrate a statistically significant detection of an asymmetry in the genus statistic between regions corresponding to low- and high-density volumes of the Universe. We attribute the asymmetry to the non-linear effects of the gravitational evolution and biased galaxy formation, and demonstrate that these effects evolve as a function of scale. We find that neither analytic prescription satisfactorily reproduces the measurements, though the weakly non-linear theory yields substantially better results at some scales, and we discuss the potential explanations for this result.
Original languageEnglish
Pages (from-to)454-466
JournalMonthly Notices of the Royal Astronomical Society
Publication statusPublished - 1 Mar 2009


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