Using cosmic voids to distinguish<i>f</i>(<i>R</i>) gravity in future galaxy surveys

Abstract

We use properties of void populations identified in N-body simulations to forecast the ability of upcoming galaxy surveys to differentiate models of f (R) gravity from cold dark matter cosmology. We analyse multiple simulation realizations, which were designed to mimic the expected number densities, volumes, and redshifts of the upcoming Euclid satellite and a lower-redshift ground-based counterpart survey, using the public VIDE toolkit. We examine void abundances, ellipicities, radial density profiles, and radial velocity profiles at redshifts 1.0 and 0.43. We find that stronger f (R) coupling strengths eliminates small voids and produces voids up to ∼20 per cent larger in radius, leading to a significant tilt in the void number function. Additionally, under the influence of modified gravity, voids at all scales tend to be measurably emptier with correspondingly higher compensation walls. The velocity profiles reflect this, showing increased outflows inside voids and increased inflows outside voids. Using the void number function as an example, we forecast that future surveys can constrain the modified gravity coupling strength to ∼3 × 10−5 using voids.