Consistency of the growth rate in different environments with the 6dF Galaxy Survey: measurement of the void-galaxy and galaxy-galaxy correlation functions

We present a new test of gravitational physics by comparing the growth rate of cosmic structure measured around voids with that measured around galaxies in the same large-scale structure data set: the low-redshift 6-degree Field Galaxy Survey. By fitting a redshift space distortion model to the two-dimensional galaxy-galaxy and void-galaxy correlation functions, we recover the growth rate values fσ8=0.42±0.06 and 0.39±0.11, respectively. The environmental dependence of cosmological statistics can potentially discriminate between modified-gravity scenarios which modulate the growth rate as a function of scale or environment and test the underlying assumptions of homogeneity and isotropy.