The WiggleZ Dark Energy Survey: the transition to large-scale cosmic homogeneity

By Morag Scrimgeour, T. Davis, C. Blake, J. B. James, Gregory B. Poole, L. Staveley-Smith, S. Brough, M. Colless, C. Contreras, W. Couch and 19 more. 2012

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We have made the largest volume measurement to date of the transition to large-scale homogeneity in the distribution of galaxies. We use the WiggleZ survey, a spectroscopic survey of over 200 000 blue galaxies in a cosmic volume of ∼1 h^(−3) Gpc^3. A new method of defining the ‘homogeneity scale' is presented, which is more robust than methods previously used in the literature, and which can be easily compared between different surveys. Due to the large cosmic depth of WiggleZ (up to z = 1), we are able to make the first measurement of the transition to homogeneity over a range of cosmic epochs. The mean number of galaxies N(< r) in spheres of comoving radius r is proportional to r^3 within 1 per cent, or equivalently the fractal dimension of the sample is within 1 per cent of D_2 = 3, at radii larger than 71 ± 8 h^(−1) Mpc at z ∼ 0.2, 70 ± 5 h^(−1) Mpc at z ∼ 0.4, 81 ± 5 h^(−1) Mpc at z ∼ 0.6 and 75 ± 4 h^(−1) Mpc at z ∼ 0.8. We demonstrate the robustness of our results against selection function effects, using a Λ cold dark matter (ΛCDM) N-body simulation and a suite of inhomogeneous fractal distributions. The results are in excellent agreement with both the ΛCDM N-body simulation and an analytical ΛCDM prediction. We can exclude a fractal distribution with fractal dimension below D_2 = 2.97 on scales from ∼80 h^(−1) Mpc up to the largest scales probed by our measurement, ∼300 h^(−1) Mpc, at 99.99 per cent confidence.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/27f6efb24b934e5d91720fc3dcffcf1e7823e2a2

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Citations in the corpus

A structure in the early Universe at z ∼ 1.3 that exceeds the homogeneity scale of the R-W concordance cosmology (2012, methodology): “While Scrimgeour et al. (2012) find a transition to homogeneity on scales ∼ 100–115 Mpc, using WiggleZ data, Sylos Labini (2011) does not, on scales up to ∼ 200 Mpc, using SDSS galaxies.”
Evidence for anisotropy of cosmic acceleration (2018, background): “Counts-in-spheres of galaxy catalogues have suggested that there is a transition to (statistical) homogeneity on scales exceeding ∼100 Mpc (Hogg et al. 2005; Scrimgeour et al. 2012), although sufficiently large volumes have not yet been surveyed to establish this definitively.”
Cosmology and Fundamental Physics with the Euclid Satellite (2012, result): “Along these lines, different groups have argued that the Universe might in fact not reach a homogeneous regime on large scales, and that instead it behaves like a fractal [331, 953, 874, 1141, 644, 1142, 1139], while other groups claim the opposite result: the predictions of the standard ΛCDM model ”
TWO MICRON ALL SKY SURVEY PHOTOMETRIC REDSHIFT CATALOG: A COMPREHENSIVE THREE-DIMENSIONAL CENSUS OF THE WHOLE SKY (2013, background): “Although tests applicable to surveys of even limited sky coverage exist (e.g. Hogg et al. 2005; Sarkar et al. 2009; Gibelyou & Huterer 2012; Marinoni et al. 2012; Scrimgeour et al. 2012), their usefulness for all-sky redshift surveys is currently limited by the shallowness of the latter.”