Tangential Large Scale Structure Evidence for a Low Density Universe

Several observational analyses suggest that matter is spatially structured at about 130 Mpc/h at low redshifts. This peak in the power spectrum provides a standard ruler in comoving space which can be used to compare the local geometry at high and low redshifts, thereby constraining the curvature parameters. It is shown here that this power spectrum peak is present in the observed quasar distribution at z∼2: qualitatively, via wedge diagrams which clearly show a void-like structure, and quantitatively, via one-dimensional Fourier analysis of the quasars' tangential distribution. The sample studied here contains 812 quasars. The method produces strong constraints (68% confidence limits) on the density parameter Ω0 and weaker constraints on the cosmological constant λ0, which can be expressed by the relation Ω0=(0.24±0.15)+(0.10±0.08)λ0. Independently of λ0 (in the range λ0∈[0,1]), the constraint is 0.1<Ω0<0.45. Combination of the present results with SN Type Ia results yields Ω0=(0.30±0.11)+(0.57±0.11)(λ0−0.7), 0.55<λ0<0.95, (68% confidence limits). This strongly supports the possibility that the observable universe satisfies a nearly flat, perturbed Friedmann-Lemaître-Robertson-Walker model, independently of any cosmic microwave background observations.