Tangential large scale structure as a standard ruler: curvature parameters from quasars
B.F. Roukema 1 and
G.A. Mamon 2,3
Received 22 November 1999 / Accepted 17 April 2000
Several observational analyses suggest that matter is spatially structured at a scale of 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 : 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 and weaker constraints on the cosmological constant , which can be expressed by the relation . Independently of (in the range ), the constraint is . Constraints if the cosmological constant is zero or if are and respectively.
The power spectrum peak method is independent from the supernovae Type Ia method by choice of astrophysical object, by redshift range, and by use of a standard ruler instead of a standard candle. Combination of the two results yields (68% confidence limits) without assuming that . 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 .
In other words it has been shown that .
Key words: cosmology: observations cosmology: theory galaxies: quasars: general cosmology: distance scale cosmology: large-scale structure of Universe reference systems
Send offprint requests to: B.F. Roukema
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© European Southern Observatory (ESO) 2000
Online publication: June 8, 2000