Waltraut C. Seitter

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.

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.

A spectroscopic survey of recurrent novae at minimum

From 1986 to 1988 optical spectroscopy near minimum of all then established recurrent novae (excluding recurrent X-ray novae such as V616 Mon and V404 Cyg) was carried out with the 3.6 m and 1.5 m telescopes of ESO, using EFOSC with CCD and the Cassegrain spectrograph with CCD or IDS, respectively. Flux-calibrated spectra of the six objects are shown in Figs, la f. The most recent recurrent nova, V745 Sco, is included in the present discussion, because 1 month after outburst it had already reached a very late stage of outburst evolution. A spectrum of V745 Sco is shown in Schwarz et al. (1989).

The Nebular Research of Carl Wirtz

We briefly review the nebular research in the 19th and early 20th century, and the role played by the newly founded Strasbourg Observatory in this field. The life of Carl Wirtz (1874–1939) is outlined. His studies in Bonn, his work in Vienna and Hamburg, his astronomical activity in Strasbourg from 1903–1916, at the war headquarters in Berlin in the following two years, and from 1919 up to his forced retirement in 1937 at Kiel University are described, both in general terms and specifically in terms of extragalactic research. His achievements were rarely recognized by his contemporaries, both because of his somewhat unusual way of presentation, and because of his “inner emigration” in the last years of his life.

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.

Flares And Flashes: The Future

I would like to thank the participants in this round-table discussion for their contributions and insights. Clearly, there are regions of overlap between the variable star observers and those looking for counterparts to GRBs. The experiments that search for counterparts to GRBs, independent of energy, have been designed to look for variability in celestial sources, and thus are “tuned” to the characteristics of “flare” and “flash” sources: these experiments may be able to contribute to the understanding of variable stars of many classes. In particular, the wide-field experiments described here should be able to provide information about the rate of rare, high-amplitude flares.

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.

The cosmological constant — historical annotations

A brief history of the cosmological constant is given. Introduced and later discussed away by Einstein, recognized for its potential of defining cosmic time and tracing the history of the universe by Friedmann, the cosmological constant was first identified with negative vacuum density by Lemaitre. His interpretation was much later revived by Gliner whose work, together with the concept of a variable cosmological “constant” discussed by Linde on the basis of unified field theories, and the work of numerous other authors laid the foundations for the role the cosmological constant was to assume later: that of the very essence of inflationary theories of the universe. The unanswered problems which appear in this context remind us that a general quantum field theory is still lacking, but also that its solution lies with the understanding of vaccum energy, i.e. of Λ.

Physical Parameters of Prenovae and Outburst Amplitudes

The best observed novae of C. Payne-Gaposchkin’s list and the brightest novae found since 1960 yield 37 data points in a diagram showing absolute magnitudes of novae at minimum light versus amplitude of the outburst. Three dwarf novae are found well separated from the novae, five recurrent novae mix with the high luminosity end of the nova sequence. Due to the small scatter in absolute magnitudes at maximum a noticeable dependence of outburst amplitude on Mmin which ranges from 9m to brighter than Om, is found. For eleven novae blue spectra at minimum indicate high temperatures. O-type temperatures and white dwarf densities are, however, mutually exclusive over a wide range of Mmin. Only two novae, CP Pup and V1500 Cyg, have, under the assumption of O-type temperatures, densities within the white dwarf range and even they are found near the low-density limit. This leaves three explanations for minimum light: 1) All prenovae are normal white dwarfs, additional light comes from a sufficiently bright blue disk. 2) All prenovae are white dwarfs with a much wider range of temperatures than hitherto assumed - up to more than a million degrees. 3) All prenovae are O-type stars with a wide range of densities. These assumptions lead, respectively, to a: 1) disk-amplitude relation; 2) temperature-amplitude relation; 3) density-amplitude relation; stating that fainter disks, lower temperatures or higher densities agree with more spectacular nova outbursts.