The challenge of large and empty voids in the SDSS DR7 redshift survey

Abstract

Context. We present catalogues of voids for the SDSS DR7 redshift survey and for Millennium I simulation mock data. Aims. We aim to compare the observations with simulations based on a ΛCDM model and a semi-analytic galaxy formation model. We use the void statistics as a test for these models. Methods. We assembled a mock catalogue that closely resembles the SDSS DR7 catalogue and carried out a parallel statistical analysis of the observed and simulated catalogue. Results. We find that in the observation and the simulation, voids tend to be equally spherical. The total volume occupied by the voids and their total number are slightly larger in the simulation than in the observation. We find that large voids are less abundant in the simulation and the total luminosity of the galaxies contained in a void with a given radius is higher on average than observed by SDSS DR7 survey. We expect these discrepancies to be even more significant in reality than found here since the present value of σ 8 given by WMAP7 is lower than the value of 0.9 used in the Millennium I simulation. Conclusions. The reason why the simulation fails to produce enough large and dark voids might be the failure of certain semi-analytic galaxy formation models to reduce the small-scale power of ΛCDM and to produce sufficient power on large scales.

On the observability of coupled dark energy with cosmic voids

“…Identifying voids with the VIDE toolkit, we find no statistically significant differences in the ellipticities, but find that coupling produces a population of significantly larger voids, possibly explaining the recent result of Tavasoli et al (2013). In addition, we use the universal density profile of Hamaus et al (2014) to quantify the relationship between coupling and density profile shape, finding that the coupling produces broader, shallower, undercompensated profiles for large voids by thinning the walls between adjacent medium-scale voids.…”

Unraveling the nature of gravity through our clumpy universe

“…Another way to put this is to say that the gravitational potential always remains at the perturbation level Φ ≤ 1, while the matter density can reach up to 10 5 for structures. There are some super-voids of up to ∼ 200M pc, where this approximation will become weaker, but as we are probing the deviation of distance moduli at low redshifts, where the maximum size of any truly empty voids (rather than that mainly due to the sparseness of the original galaxy catalog) are ∼ 30M pc in radius [13], this approximation should hold. Consequently by neglecting the κ SW and κ ISW effects, the deviation in luminosity distance ∆µ ≡ µ obs − µ ΛCDM , which is the difference between the standard cosmology distance moduli (the background) from the observational distance modulus, is sourced by convergence and peculiar velocity.…”

“…Now the crucial part of our work is the procedure that we use to extract κ g . In order to find the κ g along each line of sight to the SNe Ia we use the void catalog introduced by Tavasoli et al [13]. This catalog is based on the original algorithm of the Aikio and Maehoenen (AM) [26] method in the 3D sample.…”

“…Accordingly, we can find out about the evolution of structures over all redshift ranges from the observer to the source. In order to find the lensing/(de)lensing maps, we used a void catalog obtained by Tavasoli et al [13] to find the voids and structures in Sloan Digital Sky Survey (SDSS) data release 10 (DR10) to measure the distribution of structures and the convergence observationally. ( For more details see Tavasoli et al (2014) [14] ) The structure of this essay is: In Sec.…”

Clues on void evolution – III. Structure and dynamics in void shells

“…The voids in the galaxy distribution have been extensively e-mail: andresnicolas@oac.uncor.edu studied and characterized by several authors in a variety of wavelengths (Pellegrini et al 1989;Slezak et al 1993;Aikio & Mähönen 1998;El-Ad & Piran 2000;Müller et al 2000;Arbabi-Bidgoli & Müller 2002;Hoyle & Vogeley 2002Hoyle et al 2005;Colberg et al 2005b;Ceccarelli et al 2006;Shandarin et al 2006;Platen et al 2007;Brunino et al 2007;Hahn et al 2007;Neyrinck 2008;Foster & Nelson 2009;Lavaux & Wandelt 2010;Tavasoli et al 2013;Elyiv et al 2014) and show similar properties, even though a variety of identification methods and data samples are used (Colberg et al 2008). Also, the void phenomenon has been a target of many theoretical analysis in numerical simulations (Hoffman & Shaham 1982;Hausman et al 1983;Fillmore & Goldreich 1984;Icke 1984;Bertschinger 1985;Kauffmann & Fairall 1991;Padilla et al 2005;Aragon-Calvo et al 2010;AragonCalvo & Szalay 2013).…”