Voids in the SDSS DR9: observations, simulations, and the impact of the survey mask

We present and study cosmic voids identified using the watershed void finder vide in the Sloan Digital Sky Survey Data Release 9, compare these voids to ones identified in mock catalogues, and assess the impact of the survey mask on void statistics such as number functions, ellipticity distributions, and radial density profiles. The nearly 1000 identified voids span three nearly volume-limited samples from redshift z = 0.43 to 0.7. For comparison, we use 98 of the publicly available second-order Lagrangian perturbation theory-based mock galaxy catalogues of Manera et al., and also generate our own mock catalogues by applying a Halo Occupation Distribution model to an N-body simulation. We find that the mask reduces the number density of voids at all scales by a factor of 3 and slightly skews the relative size distributions. This engenders an increase in the mean ellipticity by roughly 30 per cent. However, we find that radial density profiles are largely robust to the effects of the mask. We see excellent agreement between the data and both mock catalogues, and find no tension between the observed void properties and the properties derived from Λcolddarkmatter simulations. We have added the void catalogues from both data and mock galaxy populations discussed in this work to the Public Cosmic Void Catalog at http://www.cosmicvoids.net.