Monday

Spectroscopic galaxy redshift surveys provide a wealth of cosmological information, in particular measurements of the angular diameter distance, Hubble rate, and growth rate of structure. We present a new method of measuring these quantities through measurement of the anisotropic cross-correlation of galaxies with cosmic voids, allowing simultaneous fits for redshift space distortions and those from Alcock-Paczynski (AP) effect. Applied to CMASS data from the Baryon Oscillation Spectroscopic Survey (BOSS) at redshift 0.57, this method yields a measure of the AP parameter that is more precise than that from BAO by a factor of 3.5, and orthogonal degeneracy directions in parameter space. We show how combining this void information with traditional BAO and galaxy clustering methods reduces measurement errors in each variable by a factor of 2, equivalent to a massive increase in the effective survey data volume. We show that in combination with cosmic microwave background measurements, this gain in cosmological information significantly tightens constraints on alternative models of dark energy over those previously obtained.