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Astron. Astrophys. 334, 404-408 (1998)

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The ESO Slice Project [ESP] galaxy redshift survey *

V. Evidence for a D=3 sample dimensionality

R. Scaramella 1, 4, L. Guzzo 2, G. Zamorani 3, 4, E. Zucca 3, 4, C. Balkowski 5, A. Blanchard 6, A. Cappi 3, V. Cayatte 5, G. Chincarini 2, 12, C. Collins 7, A. Fiorani 1, D. Maccagni 8, H. MacGillivray 9, S. Maurogordato 10, R. Merighi 3, M. Mignoli 3, D. Proust 5, M. Ramella 11 and G.M. Stirpeand G. Vettolani 3, 4

1 Osservatorio di Roma, via dell'Osservatorio 2, I-00040 Monteporzio Catone, Italy
2 Osservatorio di Brera, via Bianchi 46, I-22055 Merate, Italy
3 Osservatorio di Bologna, via Zamboni 33, I-40126 Bologna, Italy
4 I.R.A./C.N.R. via Gobetti 101, I-40129 Bologna, Italy
5 Observatoire de Paris, DAEC, Unité associée au CNRS, D0173 et à l'Université Paris 7, 5 Place J.Janssen, F-92195 Meudon, France
6 Université L. Pasteur, Observatoire Astronomique, 11 rue de l'Université, F-67000 Strasbourg, France
7 Astrophysics Research Institute, Liverpool John-Moores University, Byron Street, Liverpool L3 3AF, UK
8 Istituto di Fisica Cosmica e Tecnologie Relative, via Bassini 15, I-20133 Milano, Italy
9 Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ, UK
10 CERGA, Observatoire de la Côte d'Azur, B.P. 229, F-06304 Nice Cedex 4, France
11 Osservatorio Astronomico di Trieste, via Tiepolo 11, I-34131 Trieste, Italy
12 Università degli Studi di Milano, via Celoria 16, I-20133 Milano, Italy

Received 22 December 1997 / Accepted 2 March 1998


The issue of the approximate isotropy and homogeneity of the observable universe is one of the major topics in modern Cosmology: the common use of the Friedmann-Robertson-Walker [FWR] metric relies on these assumptions. Therefore, results conflicting with the "canonical" picture would be of the utmost importance. In a number of recent papers it has been suggested that strong evidence of a fractal distribution with dimension [FORMULA] exists in several samples, including Abell clusters [ACO] and galaxies from the ESO Slice Project redshift survey [ESP].

Here we report the results of an independent analysis of the radial density run, [FORMULA], of the ESP and ACO data.

For the ESP data the situation is such that the explored volume, albeit reasonably deep, is still influenced by the presence of large structures. Moreover, the depth of the ESP survey ([FORMULA]) is such to cause noticeable effects according to different choices of k-corrections, and this adds some additional uncertainty in the results. However, we find that for a variety of volume limited samples the dimensionality of the ESP sample is [FORMULA], and the value [FORMULA] is always excluded at the level of at least five (bootstrap) standard deviations. The only way in which we reproduce [FORMULA] is by both unphysically ignoring the galaxy k-correction and using Euclidean rather than FRW cosmological distances.

In the cluster case the problems related to the choice of metrics and k-correction are much lessened, and we find that ACO clusters have [FORMULA] and [FORMULA] for richness class [FORMULA] and [FORMULA], respectively. Therefore [FORMULA] is excluded with high significance also for the cluster data.

Key words: large-scale structure of Universe – galaxies: redshifts – galaxies: clusters

* based on observations collected at the European Southern Observatory, La Silla, Chile.

Send offprint requests to: R. Scaramella

© European Southern Observatory (ESO) 1998

Online publication: May 15, 1998