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Astron. Astrophys. 358, 395-408 (2000)


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Tangential large scale structure as a standard ruler: curvature parameters from quasars

B.F. Roukema 1 and G.A. Mamon 2,3

1 Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune, 411 007, India (boud@iucaa.ernet.in)
2 Institut d'Astrophysique de Paris (CNRS UPR 341), 98bis Bd Arago, 75014 Paris, France (gam@iap.fr)
3 DAEC (CNRS UMR 8631), Observatoire de Paris-Meudon, 5 place Jules Janssen, 92195 Meudon Cedex, France

Received 22 November 1999 / Accepted 17 April 2000

Abstract

Several observational analyses suggest that matter is spatially structured at a scale of [FORMULA] 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 [FORMULA]: 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 [FORMULA] and weaker constraints on the cosmological constant [FORMULA], which can be expressed by the relation [FORMULA]. Independently of [FORMULA] (in the range [FORMULA]), the constraint is [FORMULA]. Constraints if the cosmological constant is zero or if [FORMULA] are [FORMULA] and [FORMULA] 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 [FORMULA] [FORMULA] (68% confidence limits) without assuming that [FORMULA]. 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 [FORMULA].

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

© European Southern Observatory (ESO) 2000

Online publication: June 8, 2000

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