paper

Beyond BAO: improving cosmological constraints from BOSS with measurement of the void-galaxy cross-correlation

arXiv:1904.01030 · doi:10.1103/PhysRevD.100.023504

Abstract

We present a measurement of the anisotropic void-galaxy cross-correlation function in the CMASS galaxy sample of the BOSS DR12 data release. We perform a joint fit to the data for redshift space distortions (RSD) due to galaxy peculiar velocities and anisotropies due to the Alcock-Paczynski (AP) effect, for the first time using a velocity field reconstruction technique to remove the complicating effects of RSD in the void centre positions themselves. Fits to the void-galaxy function give a 1% measurement of the AP parameter combination $D_{A} (z) H (z) / c = 0.4367 \pm 0.0045$ at redshift $z = 0.57$ , where $D_{A}$ is the angular diameter distance and $H$ the Hubble parameter, exceeding the precision obtainable from baryon acoustic oscillations (BAO) by a factor of ~3.5 and free of systematic errors. From voids alone we also obtain a 10% measure of the growth rate, $f I ¨ _{8} (z = 0.57) = 0.501 \pm 0.051$ . The parameter degeneracies are orthogonal to those obtained from galaxy clustering. Combining void information with that from BAO and galaxy RSD in the same CMASS sample, we measure $D_{A} (0.57) / r_{s} = 9.383 \pm 0.077$ (at 0.8% precision), $H (0.57) r_{s} = (14.05 \pm 0.14) 1 0^{3}$ kms $^{- 1}$ Mpc $^{- 1}$ (1%) and $f I ¨ _{8} = 0.453 \pm 0.022$ (4.9%), consistent with cosmic microwave background (CMB) measurements from Planck. These represent a factor \sim2 improvement in precision over previous results through the inclusion of void information. Fitting a flat cosmological constant $I^$ CDM model to these results in combination with Planck CMB data, we find up to an 11% reduction in uncertainties on $H_{0}$ and $I^c ◯_{m}$ compared to use of the corresponding BOSS consensus values. Constraints on extended models with non-flat geometry and a dark energy of state that differs from $w = - 1$ show an even greater improvement.

22 pages, 15 figures. Accepted for publication in Phys.Rev.D. v2 corrects small error in likelihood analysis; minor changes to figures and text, cosmological results unchanged. Reconstruction and void-finding code available at https://github.com/seshnadathur/Revolver, likelihood analysis code available at https://github.com/seshnadathur/void-galaxy-cosmo-fitter