Peter Schuecker

The Muenster Redshift Project. III. Observational Constraints on the Deceleration Parameter

The redshift-volume test for determining the deceleration parameter q0 is applied to 89,125 galaxies with redshifts z ? 0.2 (redshift errors ?z = 0.031) and magnitudes 14.0 ? rF ? 18.0 mag, obtained within the Muenster Redshift Project (MRSP). With samples of this size, cosmic curvature effects can be measured even at intermediate redshifts. Comparatively small z-values and red photometric magnitudes assure that biased object selection and galaxy evolution do not affect the measurements in uncontrolled ways. In the first step of our analysis, the redshift-volume test assumes a minimum model of passive galaxy evolution. For the cosmological constant ? = 0 and for the evolutionary models of Rocca-Volmerange & Guiderdoni, the total sample yields the deceleration parameter q0 = 0.10 with the 95% confidence limit, q0 < 0.75. In a second step, we evaluate?within the errors of the first step?whether our q0-value is over- or underestimated, using those observed evolutionary trends that appear to be nearly q0 independent. The trends indicate that our result q0 = 0.10 can be regarded as an upper limit. Effects of incompleteness, errors in the (K + E)-corrections due to extreme galaxy mixtures, as well as different models of population synthesis, large-scale clustering, galactic reddening, and gravitational lensing, are discussed. We conclude that the combination of MRSP redshift data, observed evolutionary trends in the galaxy luminosity functions, and passive galaxy aging suggests an open universe.

Scales of structures and homogeneity in the universe

A low-resolution objective prism redshift survey of southern galaxies (15<m<20, z≤0.3) provides 46,000 redshifts with errors 0.010≤σ z ≤0.013 from which subsamples are drawn for studies of large-scale structures and scales of homogeneity in the universe. The derived mean number density for galaxies with −20.8≤M≤−19.2 is 0.024h 3 Mpc −3 in a total volume of 1.5×10 6 h −3 Mpc 3 . Maximum density deviations, tested with galaxies −20.8≤M≤−20.2 lie between 10% and 30% in comoving test volumes of 5×10 4 h −3 Mpc 3 , shifted over 10 5 h −3 Mpc 3 . The present data appear to be incompatible with the presence of 100h −1 Mpc voids

THE MUENSTER REDSHIFT PROJECT. II. THE REDSHIFT SPACE GALAXY POWER SPECTRUM

The redshift space galaxy power spectrum is estimated using magnitude-limited samples of up to 87,558 galaxies with redshifts z ≤ 0.2 and magnitudes rF ≤ 18.0 mag. Although the random redshift errors are comparatively large (σz = 0.031), the present survey sample gives reliable power spectral densities for wavenumbers 0.0125 ≤ k ≤ 0.15 h Mpc–1 corresponding to wavelengths 40 ≤ λ ≤ 500 h–1 Mpc. The Muenster Redshift Project data give a clear indication for the existence of a turnover in the shape of the power spectrum near wavelengths of 160 h–1 Mpc.

The Muenster Redshift Project

The Muenster Redshift Project is based on microdensitometer scans of pairs of direct and objective prism Schmidt plates, used for the determination of positions, magnitudes, morphological types, and low-dispersion redshifts of galaxies and quasars. From these data structural features and parameters which characterize the present universe are derived. The 0.9 million redshifts, reduced so far, permit us to take a first step towards very large-scale analysis.

Large-Scale Structures from Low-Resolution Redshift Surveys

Properties of low-resolution redshift surveys are illustrated. Two examples concerning redshifts from objective prism Schmidt plates are given: a survey with presently 568 galaxy redshifts in the Hydra-Centaurus region, b J < 18 mag, z < 0.15 and σ z = 0.0029 (based on medium spectral resolution plates from the ESO Schmidt Telescope) and the Muenster Redshift Project MRSP with presently 0.9 million galaxy redshifts, b J < 20 mag, z < 0.3, and σ z = 0.012 for more than 75% of the galaxies (based on low spectral resolution plates from the UK Schmidt Telescope). While the ESO sample is dominated by small-scale high-amplitude fluctuations, the UK sample covers a more representative part of the universe from which the large-scale low-amplitude fluctuations of galaxy number densities and the deceleration parameter q 0 of the universe can be determined.

Problems and solutions in observational cosmology

Large numbers of data permit a statistical approach to topics in observational cosmology. The derivations of cosmological and structural parameters from deeper and wider samples promise more general solutions, but pose new problems of analysis. Examples are given for the statistical derivation of the quantities Ho, q o , Ωo and A, of structural properties of clusters of galaxies, and of the evolution of clustering.