The WiggleZ Dark Energy Survey: measuring the cosmic expansion history using the Alcock-Paczynski test and distant supernovae

Abstract

Astronomical observations suggest that today's Universe is dominated by a dark energy of unknown physical origin. One of the most notable results obtained from many models is that dark energy should cause the expansion of the Universe to accelerate: but the expansion rate as a function of time has proved very difficult to measure directly. We present a new determination of the cosmic expansion history by combining distant supernovae observations with a geometrical analysis of large-scale galaxy clustering within the WiggleZ Dark Energy Survey, using the Alcock-Paczynski test to measure the distortion of standard spheres. Our result constitutes a robust and non-parametric measurement of the Hubble expansion rate as a function of time, which we measure with 10-15 per cent precision in four bins within the redshift range 0.1 < z < 0.9. We demonstrate, in a manner insensitive to the assumed cosmological model, that the cosmic expansion is accelerating. Furthermore, we find that this expansion history is consistent with a cosmological-constant dark energy.

Observational probes of cosmic acceleration

“…An AP measurement would allow the BAO measurement of D A (z) to be "transferred" to H(z), thus yielding a better measure of the dark energy contribution. Blake et al (2011c) have recently implemented a similar idea by using their AP measurements in the WiggleZ survey to convert SN luminosity distances into H(z) determinations.…”

“…AP measurements provide a cosmological test in their own right, and they allow high-redshift distance measurements to be translated into constraints on H(z), which is a more direct measure of energy density. Recently Blake et al (2011c) have measured the AP parameter H(z)D A (z) from galaxy clustering in the WiggleZ survey, obtaining 10 − 15% precision in each of four redshift bins out to z = 0.8, and Reid et al (2012) have obtained ∼ 6% precision at z = 0.55 from BOSS galaxies, improving to ∼ 3.5% if they assume that the growth rate (and hence the peculiar velocity distortion) has the value predicted by ΛCDM. Both results are consistent with flat-Λ geometry for WMAP7 values of Ω m .…”

The observational status of Galileon gravity after Planck

“…[60], but scaled down by a constant factor to match approximately the amplitude of the best-fitting νCubic (PLB) model. In the lower panels, the data points show the measurements extracted by using the data from the 2dF [65] (square), 6dF [66] (triangle), SDSS DR7 (LRG) [67] (circle), BOSS [68] (dot) and WiggleZ [69] (side triangles) galaxy surveys. of temperature) as it comes out of it.…”

“…2 show the time evolution of f σ 8 in the best-fitting models (computed using linear theory), together with the measurements from the 2dF [65] (square), 6dF [66] (triangle), SDSS DR7 (LRG) [67] (circle), BOSS [68] (dot) and WiggleZ [69] (side triangles). In principle, these data can be used to further constrain the νCubic model.…”

First experimental constraints on the disformally coupled Galileon model

“…f σ 8 (z) and the Alcock-Paczynski parameter F(z), mainly from Percival et al (2004), Blake et al (2011), Beutler et al (2012, Samushia et al (2012a), Reid et al (2012). For the cosmic microwave background (CMB), we updated our analysis to use the WMAP9 distance priors (Hinshaw et al 2012) instead of the WMAP7 ones (Komatsu et al 2011).…”