The observational material is based upon pencil-beam surveys made with the NRAO 300-ft radio telescope at 1400 MHz. the GB survey (Maslowski 1972) covers 0.1586 sr in the zone 7h15m ≦ α ≦ 16h20m, 45°.9 ≦ δ < 51°.8. the GB2 survey made by Machalski in 1975 was carried out in the region defined by 7h08m ≦ α ≦ 16h58m, 31°.8 ≦ α 39°.6 (0.2828 sr).

The first quantitative evidence for a large scale density excess or “metagalactic cloud” including the Local Group was obtained by Holmberg (1937) and confirmed by Reiz (1941). the present concept of the Local Supercluster (LSC) as a flattened aggregate of field galaxies, small groups and larger clouds centered at the Virgo cluster was formulated 25 years ago (de Vaucouleurs 1953) even before large-scale superclustering was recognized as a general phenomenon. See review papers in Vistas in Astronomy (1956), Soviet Astronomy (1960), Science (1970), Publ. Astron. Soc. Pacific (1971), and IAU Symp. No. 63 (Abell 1974).

To complement our movie, we offer three steroscopic pictures of a region enclosing the Local Supercluster. A coordinate system is defined.

In 1924 Hubble presented the first generally convincing evidence, from the identification of variable stars, that some of the brightest “spiral nebulae” are galaxies of stars well outside the bounds of our own Galaxy. This led him to reconsider the idea that the faint “spiral nebulae,” which were known to be much more abundant than bright ones, might be similar objects at greater distances.

I would like to describe in a few words work which was done by Zeldovich and myself. It gives some restrictions on the amplitude of possible very large-scale density fluctuations mentioned by Peebles. the main question investigated in this work is the following. What can be said, using known observational data and some general hypotheses, about structure of the Universe beyond the region accessible for observation at the present epoch? in fact we consider density fluctuations (as well as rotational perturbations and gravitational waves) with wavelengths larger than the horizon. We use the observational fact that the quadrupole-type anisotropy of the microwave background radiation is absent at the level of δT/T < 10−4. It is interesting to know if it may happen that, at the present epoch, there exists a significant density of perturbations (say, with the dimensionless amplitude of the order of 10−1) which we do not even suspect because the corresponding wavelength is very long and therefore direct observation of the entire perturbation is not possible. Such a direct observation will be possible only in the remote future when the horizon becomes equal to the corresponding wavelength. To answer the question we make a natural but very important assumption. Namely, we assume that the harmonic perturbations of different wavelengths are not correlated in any particular way. Otherwise, they might fit together in such a way that all perturbations (and, therefore, δT/T) would be especially small within the horizon while significant perturbations could take place just beyond the horizon. A situation of this kind would imply that an observer at the Earth occupies a unique position in the Universe. We assume, on the contrary, that all observers are equivalent. All of them, even causally unconnected observers, could detect similar restrictions on the anisotropy of the microwave background, δT/T < 10−4. Nevertheless, the question still exists whether small perturbations unnoticeable by every observer within his horizon can represent different parts of a significant long wavelength limit. the main result of this investigation can be formulated in the following way. the observational data on δT/T in combination with the natural hypothesis on the statistical independence of different harmonics leads to the conclusion that in the Universe there are no significant (i.e. with the amplitude exceeding δT/T) density fluctuations on any spatial scale larger than the horizon. (The paper will be published in Astr. Zh. U. S. S. R. j November-December, 1977.

The phenomenon of clustering of galaxies was known earlier than the nature of the so called extragalactic nebulae. It was discovered as early as the end of XVIII century by W. Herschel and confirmed by his followers. After the introduction of Schmidt cameras into astronomy, Zwicky suggested that all galaxies participate in clustering. After the discovery of extragalactic radio sources some astronomers have been trying, in different ways, to apply the concept of clustering to them also.

As demonstrated by de Vaucouleurs (1956, 1975a, b, 1976), Abell (1961), Karachentsev (1966), Kiang and Saslaw (1969) and others, clusters of galaxies as well as groups of galaxies have a tendency to form second-order clusters of galaxies, often called superclusters. Recent statistical studies by the Princeton group (Davis, Groth and Peebles 1977, Seldner and Peebles 1977a) have confirmed this result. Statistical studies, however, give little information about the internal structure of second-order clusters.

Holmberg's (1937) analysis of the distribution of double and multiple galaxies provided what may have been the first hint of a local inhomogeneity of greater scale than that of the Local Group. the idea of a Local Supercluster was subsequently revived by de Vaucouleurs (1953, 1956, 1958). the analyses of others, as well as the continuing study of de Vaucouleurs himself (1976 and references cited therein) have now effectively established the reality of the Local Supercluster. Several other more remote inhomogeneities, or “clouds” of galaxies, were described by Shane and Wirtanen (1954). the writer (Abell 1958) found the distribution of rich clusters to be clumpy, and published a finding list of several apparent superclusters (Abell 1961).

Counts by Shane and Wirtanen detected a cloud of Galaxies - the Hercules Supercluster - centered at about α = 16h02m; δ = 17°00m. It is unclear whether there is a physical connection with another cloud located to the south for which no radial velocities are yet available and with the system A2197/A2199 located to the north. the latter is at slightly smaller redshift (velocities between 8000–11,000 km sec−1) than the Hercules cluster.

It has long been assumed that clusters of galaxies merge into a smooth “field” of isolated galaxies. Early estimates put 50% of all galaxies into the field. Using new redshift surveys over large areas we find the real distribution of galaxies to be very different. Nearly all galaxies are in clusters or groups covering a range of at least 1000 in mass and richness.

We have assembled a catalog of radial velocities and magnitudes on a homogeneous system (the corrected Harvard, B(o) magnitudes of de Vaucouleurs) for over 4000 galaxies. Using this catalog, we have compiled a magnitude limited sample of ~ 1000 galaxies with nearly complete radial velocity data. the magnitude limit is 13.0 and the galaxies are primarily from the Shapley-Ames catalog plus a few low and high surface brightness objects properly included in a magnitude limited sample. My colleagues, M. Davis, M. Geller and I are presently analyzing the dynamical properties of this sample. I would like to briefly describe a new determination of the field luminosity function and density plus our initial experiments with the use of a redshift catalog to select groups of galaxies.

The distribution of Markarian galaxies in annular zones at different angular distances θ (degrees) from the centre of the Coma cluster is shown in the Table. the coordinates of the centre for the equinox 1950 are assumed to be α = 12h57m.5, δ = 28°15′. the third, fourth and fifth columns of the Table contain the number of Markarian galaxies in each zone, the solid angle in square degrees and their mean surface densities respectively. It can be seen that an excess surface density of Markarian galaxies exists not only in the very central zone I but in the annular zone II as well. Indeed, the ratio n/ω in zone II is more than twice the value corresponding to the whole area surveyed (and to zones III and IV).

Lists I-IX of Markarian galaxies have been used as the basic observational material. An attempt has been made to form a statistically complete sample. Two regions (region I 6h.8 < α < 14h.2, 41° < δ < 77°, region II 6h.8 < α < 13h.9, 5° < δ < 32°) which appeared to be roughly complete have been carefully examined. After preliminary tests the first two hours in R.A. of the region II were removed from the analysis. the method of statistical reduction (Flin et al. 1974, A. Zieba 1975) and the maximum likelihood estimate of the number-magnitude counts (Crawford et al. 1970) were applied as a combined test in their practical version (Urbanik 1976, 1977). We have examined the whole region, as well as a number of smaller sub-regions varying in size and position. the angular sizes investigated ranged from 1° up to 30°. Our analysis of 15 galaxy sets led to the following conclusions.

A new type of catalogue of extragalactic objects is nearing completion in our department. the catalogue is on magnetic tape and is a compilation of data for galaxies and cluster of galaxies, together with references, and for counts of galaxies. At present this Metacatalogue contains about 3 × 105 entries - Abell and Zwicky clusters, Zwicky galaxies, Lick counts, Jagellonian counts and some others. the first two files of the catalogue can be obtained on request from the Centre de Données Stellaire at Strasbourg.

Groups. Even if real groups did not exist, the investigation of large regions of the sky will reveal other dense clumpings of galaxies. the usual estimate of the number of optical members in these clumpings will confirm their reality. But let us remember that all these groups are false. False groupings of galaxies should emerge in large numbers because of the effects of interstellar absorption and of variability of the observating conditions. Statistical considerations of the groups detected by Turner and Gott (1976, Ap. J., Suppl. Ser., 32, 409) leads to the conclusion that the percentage of false groups members is equal to 40% or more.

The two point correlation function w(θ) has been evaluated for the galaxies measured by the COSMOS machine at the Royal Observatory, Edinburgh, in an area of about 2 square degrees on a 2 hour exposure J plate and a 2 hour exposure R plate (Phillipps, S., Fong, R., Ellis, R.S., Fall, S.M. and MacGillivray, H.T., 1977, Mon. Not. R. astr. Soc., in press). in each case w(θ) is found to be in agreement with the form w = Aθ−0.8 found previously by Peebles and coworkers. Since the samples are not magnitude limited the selection function, i.e. the distribution in distance, was determined by using models of the galaxy distribution to fit the observed angular diameter counts. However, when these selection functions are used to scale the amplitudes found for our samples, the amplitudes are found to be lower than those expected from Peebles' results by a factor of about 3. We consider that this is likely to be due to a lack of clusters in the small area of sky which we have studied: analysis of further areas should show whether this is the case.

Tammann: The question of the mean mass density in the Universe has been mentioned many times and the organisers thought it would be useful to look at future prospects for obtaining improved estimates of Ω. the methods may be split into two types. First, the conventional methods involve determining the luminosity density in the Universe and multiplying by an appropriate mass-to-luminosity ratio. It must be emphasised that the mass determinations are dynamical and that most of the mass is not visible. There is good agreement among independent workers about the luminosity density and this figure seems to be known within a factor of 2. the appropriate mean value of M/L is more controversial, values between 10 and 200 having been discussed in the preceding lectures. It is agreed, however, that if the mean value of M/L lies in this range, one cannot close the Universe. Perhaps one should be more cautious and say that even granted the uncertainties in the quantities involved, it is unlikely that the Universe is closed.

The first evidence that quasars exhibit a non-uniform distribution in the universe was obtained ten years ago from a sample of 33 quasars in the 3CR catalogue. Much larger samples of radio quasars are now available and we will discuss the results in terms of an exponential decrease of quasar numbers with cosmic time. Only a few samples of optically selected quasars exist. We will show that their counts indicate a non-uniform space distribution, even if the redshifts are non-cosmological.

A knowledge of the surface density of quasars as a function of magnitude is important for two reasons. Firstly it is necessary in order to assess the possible statistical significance of close pairs of quasars or the association between quasars and bright galaxies. Secondly it is a necessary step in the determination of the space density or luminosity function of QSOs. We have carried out what we believe to be currently the most comprehensive investigation into the surface density of quasars. Three techniques have been used in this investigation. These are

I would like to give the first results of a survey programme for high redshift quasars and related objects on the Tautenburg-Schmidt plates. It is known that objective prism plates are very useful for detecting these objects. the smaller the dispersion of the spectra, the fainter are the objects that can be found. Our Schmidt correcting lens gives spectra with the dispersion of 2500 Å mm−1 at Hγ. the limiting magnitude is about 19m in the B range. At this very low dispersion reliable classification of the objects requires the extraction of all the information stored on the plate. That means that a quantitative evaluation should supplement visual insepction.