The 2dF Galaxy Redshift Survey: power-spectrum analysis of the final data set and cosmological implications

Abstract

We present a power-spectrum analysis of the final 2dF Galaxy Redshift Survey (2dFGRS), employing a direct Fourier method. The sample used comprises 221 414 galaxies with measured redshifts. We investigate in detail the modelling of the sample selection, improving on previous treatments in a number of respects. A new angular mask is derived, based on revisions to the photometric calibration. The redshift selection function is determined by dividing the survey according to rest-frame colour, and deducing a self-consistent treatment of k-corrections and evolution for each population. The covariance matrix for the power-spectrum estimates is determined using two different approaches to the construction of mock surveys, which are used to demonstrate that the input cosmological model can be correctly recovered. We discuss in detail the possible differences between the galaxy and mass power spectra, and treat these using simulations, analytic models and a hybrid empirical approach. Based on these investigations, we are confident that the 2dFGRS power spectrum can be used to infer the matter content of the universe. On large scales, our estimated power spectrum shows evidence for the 'baryon oscillations' that are predicted in cold dark matter (CDM) models. Fitting to a CDM model, assuming a primordial n s = 1 spectrum, h = 0.72 and negligible neutrino mass, the preferred parameters are m h = 0.168 ± 0.016 and a baryon fraction b / m = 0.185 ± 0.046 (1σ errors). The value of m h is 1σ lower than the 0.20 ± 0.03 in our 2001 analysis of the partially E-mail: shaun.cole@durham.ac.uk C 2005 RAS 506 S. Cole et al.complete 2dFGRS. This shift is largely due to the signal from the newly sampled regions of space, rather than the refinements in the treatment of observational selection. This analysis therefore implies a density significantly below the standard m = 0.3: in combination with cosmic microwave background (CMB) data from the Wilkinson Microwave Anisotropy Probe (WMAP), we infer m = 0.231 ± 0.021.

Observational probes of cosmic acceleration

“…In 2003, several papers appeared discussing the acoustic scale as a standard ruler for the measurement of dark energy in higher redshift galaxy surveys (Eisenstein, 2002;Blake and Glazebrook, 2003;Hu and Haiman, 2003;Linder, 2003;Seo and Eisenstein, 2003). Compelling detections in 2005 intensified these plans (Cole et al, 2005;Eisenstein et al, 2005), with several observational surveys proposed and numerous theoretical investigations. The rapid development of the theory led to the DETF featuring BAO as one of the four leading methods for the study of dark energy (Albrecht et al, 2006).…”

“…However, scale-dependence of bias at the 10-20% level can persist to quite low k, especially for luminous, highly biased galaxy populations, and the effective "shot noise" contribution to P gg (k) can differ from the naive 1/n g term expected for Poisson statistics ). Combinations of CMB power spectrum measurements with galaxy power spectrum measurements can yield tighter cosmological parameter constraints than either one in isolation (e.g., Cole et al 2005;Reid et al 2010). In particular, this combination provides greater leverage on the Hubble constant h, since CMB-constrained models predict galaxy clustering in Mpc while galaxy redshift surveys measure distances in h −1 Mpc (or, equivalently, in km s −1 ).…”

“…However, the first convincing detections of BAO came in 2005 from the SDSS Data Release 3 (DR3) and final 2dFGRS samples Cole et al, 2005). Eisenstein et al (2005) measured the large-scale correlation function of SDSS LRGs in the redshift range 0.16 < z < 0.47 over 3,816 square degrees, finding the acoustic peak with 3.4 σ significance.…”

“…(Recall that we use D A to denote the comoving angular diameter distance.) Cole et al (2005) measured the power spectrum of 2dFGRS galaxies in the redshift range 0 < z < 0.3 over 1,800 square degrees. The cosmological fitting analysis detected a baryon fraction of Ω b /Ω m = 0.185± 0.046, the non-zero result indicating a detection of the BAO.…”

Constraining the relative velocity effect using the Baryon Oscillation Spectroscopic Survey

“…Measurements of the baryon acoustic scale in the distribution of galaxies have established themselves as one of the most powerful tools for precision cosmology (Eisenstein, Hu & Tegmark 1998;Percival et al 2001;Blake & Glazebrook 2003;Hu & Haiman 2003;Seo & Eisenstein 2003;Linder 2003;Eisenstein et al 2005;Cole et al 2005;Beutler et al 2011;Blake et al 2011;Alam et al 2016). With the most recent measurements of the BAO scale in the BOSS survey we have now reached 1% precision in two redshift bins (Alam et al 2016;Beutler et al 2016a;Ross et al 2016).…”