Counting voids to probe dark energy

Abstract

We show that the number of observed voids in galaxy redshift surveys is a sensitive function of the equation of state of dark energy. Using the Fisher matrix formalism we find the error ellipses in the w0 − wa plane when the equation of state of dark energy is assumed to be of the form wCP L(z) = w0 + waz/(1 + z). We forecast the number of voids to be observed with the ESA Euclid satellite and the NASA WFIRST mission, taking into account updated details of the surveys to reach accurate estimates of their power. The theoretical model for the forecast of the number of voids is based on matches between abundances in simulations and the analytical prediction. To take into account the uncertainties within the model, we marginalize over its free parameters when calculating the Fisher matrices. The addition of the void abundance constraints to the data from Planck, HST and supernova survey data noticeably tighten the w0 − wa parameter space. We thus quantify the improvement in the constraints due to the use of voids and demonstrate that the void abundance is a sensitive new probe for the dark energy equation of state.

Cluster–void Degeneracy Breaking: Dark Energy, Planck, and the Largest Cluster and Void

“…While there is no consensus on the normalization of the dark-matter void MF, its shape is relatively well-understood for large supervoids. The same applies to voids defined by biased tracers, such as galaxies, provided that d v is calibrated to survey specifications (Pisani et al 2015). The radius and density contrast defined from tracers are larger than corresponding dark-matter quantities.…”

“…This is due to the different ways in which scales R L are determined: for clusters, R L is derived from the measured mass and W ; m for voids, R L is derived from the measured angular/radial extent and depends geometrically on W m (Pisani et al 2015). Degeneracies are also determined by sensitivity to proper distance (volume increase) and power-spectrum normalization and growth.…”

“…The use of void abundances to constrain s 8 and W h m was discussed by Betancort-Rijo et al (2009), but they did not derive constraints nor study the complementarity with cluster abundances. Pisani et al (2015) explored future dark-energy constraints from void abundances and qualitatively argued for complementarity with cluster abundances. A joint cluster-void analysis and real-data cosmological parameter inference based on void abundance is still outstanding.…”

“…As sensitive probes of the statistics of the matter distribution, they are useful tools for testing cosmological models. The abundances of clusters and voids are sensitive probes of dark energy (Allen et al 2011;Pisani et al 2015), modified gravity (Allen et al 2011;Lam et al 2015), neutrino properties (Brandbyge et al 2010;Massara et al 2015), and non-Gaussianity (Chongchitnan & Silk 2010).…”

A Cosmic Void Catalog of SDSS DR12 BOSS Galaxies

“…Voids also contain information on the structure formation history and cosmological scenario. The size and shape distribution of voids, their intrinsic structure, and their counts can provide insights into the growth of structure (Jennings et al 2013) and dark energy (Lee & Park 2009;Biswas et al 2010;Bos et al 2012;Pisani et al 2015). Moreover, the Alcock-Paczyński test (Alcock & Paczynski 1979) can be applied to "stacked" voids to probe the expansion history of the universe (Ryden 1995;Lavaux & Wandelt 2012;Sutter et al 2012a).…”