Cosmology with photometric redshift surveys

Abstract

We explore the utility of future photometric redshift imaging surveys for delineating the large-scale structure of the Universe, and assess the resulting constraints on the cosmological model. We perform two complementary types of analysis: (1) We quantify the statistical confidence and the accuracy with which such surveys will be able to detect and measure characteristic features in the clustering power spectrum such as the acoustic oscillations and the turnover, in a 'model-independent' fashion. We show for example that a 10,000 deg^2 imaging survey with depth r = 22.5 and photometric redshift accuracy dz/(1+z) = 0.03 will detect the acoustic oscillations with 99.9% confidence, measuring the associated preferred cosmological scale with 2% precision. Such a survey will also detect the turnover with 95% confidence, determining the corresponding scale with 20% accuracy. (2) By assuming a Lambda-CDM model power spectrum we calculate the confidence with which a non-zero baryon fraction can be deduced from such future galaxy surveys. We quantify 'wiggle detection' by calculating the number of standard deviations by which the baryon fraction is measured, after marginalizing over the shape parameter. This is typically a factor of four more significant (in terms of number of standard deviations) than the 'model-independent' result. We conclude that the precision with which the clustering pattern may be inferred from future photometric redshift surveys will be competitive with contemporaneous spectroscopic redshift surveys, assuming that systematic effects can be controlled. We also note that an analysis of Luminous Red Galaxies in the Sloan Digital Sky Survey may yield a marginal detection of acoustic oscillations in the imaging survey, in addition to that recently reported for the spectroscopic component.Comment: 23 pages, 22 figures, version accepted by MNRA

Observational probes of cosmic acceleration

“…Worse precision causes catastrophic degradation because the oscillations in angular power at the front and back of the photometric redshift slab fall out of phase. Redshift precision of 3-4% yields poor constraints on the BAO per unit volume, with a rule of thumb that one needs ten times more volume for a photometric redshift survey than a spectroscopic survey (Blake and Bridle, 2005;Seo and Eisenstein, 2007). Better redshift precision reduces this gap.…”

Simultaneous measurement of cosmology and intrinsic alignments using joint cosmic shear and galaxy number density correlations

“…In Appendix C we extend observational results for the normalisation and redshift scaling of the galaxy redshift distribution (29) by Blake & Bridle (2005) to provide a fitting formula for the luminosity function slope as a function of redshift and survey magnitude limit.…”

“…We set Σ 0 andz as a function of survey depth making use of Table 1 of Blake & Bridle (2005) where we find good fits using Σ 0, c = 9.83, η Σ = 19,z c = 0.39 andz m = 0.055. This allows us to extrapolate beyond the range of their Table, which stops at r lim = 24.…”

“…To compute the lensing magnification signal, we need to model the power-law slope of the cumulative galaxy luminosity function at the magnitude limit of the galaxy number density samples under consideration. We base our modelling on Blake & Bridle (2005) who have determined galaxy redshift distributions for a given magnitude limit, using COMBO-17 luminosity functions for the SDSS r filter (Wolf et al 2003).…”

“…In doing so we incorporate several cosmological signals which have been considered before as promising probes of cosmology themselves, including galaxy clustering from photometric redshift surveys (Blake & Bridle 2005;Dolney et al 2006;Zhan 2006;Blake et al 2007;Padmanabhan et al 2007) galaxy-galaxy lensing (e.g. Schneider & Rix 1997;Guzik & Seljak 2001Seljak 2002;Seljak et al 2005;Yoo et al 2006;Johnston et al 2007;Cacciato et al 2009) and lensing magnification (Broadhurst et al 1995;Zhang & Pen 2005, 2006van Waerbeke 2010).…”