Volume 86, Number 4, May 2009
Article Number 49001
Number of page(s) 6
Section Geophysics, Astronomy and Astrophysics
Published online 22 May 2009
EPL, 86 (2009) 49001
DOI: 10.1209/0295-5075/86/49001

Absence of self-averaging and of homogeneity in the large-scale galaxy distribution

F. Sylos Labini1, 2, N. L. Vasilyev3, L. Pietronero2, 4 and Y. V. Baryshev3

1   Museo Storico della Fisica e Centro Studi e Ricerche Enrico Fermi - Piazzale del Viminale 1, 00184 Rome, Italy, EU
2   Istituto dei Sistemi Complessi CNR - Via dei Taurini 19, 00185 Rome, Italy, EU
3   Institute of Astronomy, St. Petersburg State University - Staryj Peterhoff, 198504, St. Petersburg, Russia
4   Dipartimento di Fisica, Università di Roma “Sapienza” - Piazzale Aldo Moro 2, 00185 Rome, Italy, EU

received 6 April 2009; accepted in final form 24 April 2009; published May 2009
published online 22 May 2009

The properties of the galaxy distribution at large scales are usually studied using statistics which are assumed to be self-averaging inside a given sample. We present a new analysis able to quantitatively map galaxy large-scale structures while testing for the stability of average statistical quantities in different sample regions. We find that the newest samples of the Sloan Digital Sky Survey provide unambiguous evidence that galaxy structures correspond to large-amplitude density fluctuations at all scales limited only by sample sizes. The two-point correlations properties are self-averaging up to approximately 30 Mpc/h and are characterized by a fractal dimension D = 2.1$\pm$0.1. Then at all larger scales probed density fluctuations are too large in amplitude and too extended in space to be self-averaging inside the considered volumes. These inhomogeneities are compatible with a continuation of fractal correlations but incompatible with: i) a homogeneity scale smaller than 100 Mpc/h, ii) predictions of standard theoretical models, iii) mock galaxy catalogs generated from cosmological N-body simulations.

98.80.-k - Cosmology.
05.40.-a - Fluctuations phenomena, random processes, noise, and Brownian motion.
02.50.-r - Probability theory, stochastic processes, and statistics.

© EPLA 2009