The detectability of baryonic acoustic oscillations in future galaxy surveys

Abstract

We assess the detectability of baryonic acoustic oscillation (BAO) in the power spectrum of galaxies using ultralarge volume N-body simulations of the hierarchical clustering of dark matter and semi-analytical modelling of galaxy formation. A step-by-step illustration is given of the various effects (non-linear fluctuation growth, peculiar motions, non-linear and scaledependent bias) which systematically change the form of the galaxy power spectrum on large scales from the simple prediction of linear perturbation theory. Using a new method to extract the scale of the oscillations, we nevertheless find that the BAO approach gives an unbiased estimate of the sound horizon scale. Sampling variance remains the dominant source of error despite the huge volume of our simulation box (=2.41 h −3 Gpc 3 ). We use our results to forecast the accuracy with which forthcoming surveys will be able to measure the sound horizon scale, s, and, hence constrain the dark energy equation of state parameter, w (with simplifying assumptions and without marginalizing over the other cosmological parameters). Pan-STARRS could potentially yield a measurement with an accuracy of s/s = 0.5-0.7 per cent (corresponding to w ≈ 2-3 per cent), which is competitive with the proposed WFMOS survey ( s/s = 1 per cent w ≈ 4 per cent). Achieving w 1 per cent using BAO alone is beyond any currently commissioned project and will require an all-sky spectroscopic survey, such as would be undertaken by the SPACE mission concept under proposal to ESA.

Observational probes of cosmic acceleration

“…Small-scale structure grows non-linearly, peculiar velocities behave differently from their linear prediction, and galaxies trace the dark matter in a complicated manner. We should worry that these effects might modify the location of the BAO feature relative to the prediction of linear theory, thus distorting our standard ruler (Meiksin et al, 1999;Seo and Eisenstein, 2005;Angulo et al, 2005;Springel et al, 2005;Jeong and Komatsu, 2006;Huff et al, 2007;Angulo et al, 2008;Wagner et al, 2008).…”

“…However, any realistic bias relation must be at least somewhat non-linear, which alters the relative weighting of overdense and underdense regions and should shift the acoustic scale at second order. Early work attempted to measure this shift in simulations (Seo and Eisenstein, 2003;Angulo et al, 2008), but the volume of the simulations was insufficient to get a conclusive detection of the effect. More recently, explored galaxy bias as the ratio of the second-order to first-order bias term, finding shifts of a few tenths of a percent for reasonable bias cases.…”

Simulations of Dark Energy Cosmologies

“…The value of In Fig. 3.16 and 3.17 we plot the z = 0 and z = 3 power spectra in the AS and SUGRA models divided by a linear theory ΛCDM reference spectrum which has been smoothed using the coarse rebinning method proposed by Percival et al (2007) and refined by Angulo et al (2008). After dividing by this smoothed power spectrum, the acoustic peaks are more visible in the quasi-linear regime.…”

Luminosity Bias: From Haloes to Galaxies

“…Furthermore, the shape of these curves is different from that corresponding to the nonlinear matter power spectrum divided by the linear theory spectrum (shown by the dashed line). Reproduced from Angulo et al (2008).…”

“…Formally, the bias factor should be applied to the linear power spectrum of matter fluctuations. Angulo et al (2008) investigated this hypothesis with a moderate resolution N-body simulation of a very large cosmological volume,…”