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Astron. Astrophys. 344, 387-392 (1999)

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Comment on the paper "The ESO Slice Project galaxy redshift survey: V. Evidence for a D=3 sample dimensionality"

M. Joyce 1,2,3, M. Montuori 1, F. SylosLabini 1,4 and L. Pietronero 1

1 INFM Sezione Roma 1, Dip. di Fisica, Universitá "La Sapienza", P.le A. Moro 2, I-00185 Roma, Italy
2 INFN Sezione Roma 1
3 School of Mathematics, Trinity College, Dublin 2, Ireland
4 Dépt. de Physique Théorique, Université de Genève, 24, Quai E. Ansermet, CH-1211 Genève, Switzerland

Received 15 May 1998 / Accepted 19 January 1999


In a recent analysis of number counts in the ESP survey Scaramella et al. (1998) claim to find evidence for a cross-over to homogeneity at large scales, and against a fractal behaviour with dimension [FORMULA]. In this comment we note firstly that, if such a cross-over exists as described by the authors, the scale characterizing it is [FORMULA]. This invalidates the "standard" analysis of the same catalogue given elsewhere by the authors which results in a "correlation length" of only [FORMULA]. Furthermore we show that the evidences for a cross-over to homogeneity rely on the choice of cosmological model, and most crucially on the so called K corrections. We show that the [FORMULA] behaviour seen in the K-corrected data of Scaramella et al. is in fact unstable, increasing systematically towards [FORMULA] as a function of the absolute magnitude limit. This behaviour can be quantitatively explained as the effect of unphysical K-correction in the relevant range of red-shift ([FORMULA]). A more consistent interpretation of the number counts is that D is in the range [FORMULA], depending on the cosmological model, consistent with the continuation of the fractal [FORMULA] behaviour observed at scales up to [FORMULA]. This implies a smaller K-correction. Given, however, the uncertainty in the effect of intrinsic fluctuations on the number counts statistic, and its sensitivity on these large scales to the uncertain K corrections, we conclude that it is premature to put a definitive constraint on the galaxy distribution using the ESP data alone.

Key words: cosmology: observations – cosmology: large-scale structure of Universe

© European Southern Observatory (ESO) 1999

Online publication: March 18, 1999