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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
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 . In this comment we note firstly that, if such a cross-over exists as described by the authors, the scale characterizing it is . This invalidates the "standard" analysis of the same catalogue given elsewhere by the authors which results in a "correlation length" of only . 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 behaviour seen in the K-corrected data of Scaramella et al. is in fact unstable, increasing systematically towards 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 (). A more consistent interpretation of the number counts is that D is in the range , depending on the cosmological model, consistent with the continuation of the fractal behaviour observed at scales up to . 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