Cosmological parameters from SDSS and WMAP

Abstract

We measure cosmological parameters using the three-dimensional power spectrum P (k) from over 200,000 galaxies in the Sloan Digital Sky Survey (SDSS) in combination with WMAP and other data. Our results are consistent with a "vanilla" flat adiabatic ΛCDM model without tilt (ns = 1), running tilt, tensor modes or massive neutrinos. Adding SDSS information more than halves the WMAP-only error bars on some parameters, tightening 1σ constraints on the Hubble parameter from h ≈ 0.74−0.03 , on the matter density from Ωm ≈ 0.25 ± 0.10 to Ωm ≈ 0.30 ± 0.04 (1σ) and on neutrino masses from < 11 eV to < 0.6 eV (95%). SDSS helps even more when dropping prior assumptions about curvature, neutrinos, tensor modes and the equation of state. Our results are in substantial agreement with the joint analysis of WMAP and the 2dF Galaxy Redshift Survey, which is an impressive consistency check with independent redshift survey data and analysis techniques. In this paper, we place particular emphasis on clarifying the physical origin of the constraints, i.e., what we do and do not know when using different data sets and prior assumptions. For instance, dropping the assumption that space is perfectly flat, the WMAP-only constraint on the measured age of the Universe tightens from t0 ≈ 16.3 +2.3 −1.8 Gyr to t0 ≈ 14.1Gyr by adding SDSS and SN Ia data. Including tensors, running tilt, neutrino mass and equation of state in the list of free parameters, many constraints are still quite weak, but future cosmological measurements from SDSS and other sources should allow these to be substantially tightened.

Beyond the cosmological standard model

“…23 As in the X − X 2 case, there is a crossover between two qualitatively different behaviors; far from the source the field profile will have the usual Coulomb ∼ 1/r form, while near the source, the force will be suppressed relative to gravity. This crossover between these two behaviors happens when X/Λ 4 ∼ 1, the same scale as (6.8)…”

“…Indeed, in the last decade the basic parameters of the accelerating universe are well measured even without using supernova data-providing a powerful consistency check. The two other powerful methods that have been used to measure the geometry of the universe are: the cosmic microwave background (CMB) [13][14][15][16][17][18][19][20][21][22] and the Baryonic Acoustic Oscillation (BAO) feature in the galaxy power spectrum [23][24][25][26][27][28][29][30]. In fact, since measurement of q 0 only constrains the linear combination 1 2 Ω m − Ω Λ , these measurements are a very powerful tool in breaking the degeneracy between these two parameters.…”

“…There is overwhelming observational evidence that the universe is undergoing accelerated expansion from observations of type Ia supernovae [1][2][3][4][5][6][7][8][9][10][11][12], from Cosmic Microwave Background measurements [13][14][15][16][17][18][19][20][21][22], and from detailed studies of large-scale structure [23][24][25][26][27][28][29][30]. All of the measurements are in good agreement, with all data consistent with a Λ-cold dark matter (ΛCDM) cosmology [31,32], with a value of the cosmological constant of about Λ obs.…”

Neutrino masses and cosmic radiation density: combined analysis

“…[3]. We use distant type Ia supernovae measured by the SuperNova Legacy Survey (SNLS) [9] and large-scale structure data from the 2dF [10] and SDSS [11,12] surveys. From the SDSS we also include the recent measurement of the baryon acoustic oscillation feature in the 2-point correlation function [13].…”

A new mechanism for dark energy: the adaptive screening

“…10 −3 eV [1][2][3][4][5][6][7][8][9][10][11]. The same measurements allow for the suggestive interpretation of dark energy as a small but non-vanishing pure vacuum energy: the famous cosmological constant, for which w = −1 must hold at all times.…”