Large scale correlations in galaxy clustering from the Two degree Field Galaxy Redshift Sur.pdf

a r X i v : a s t r o - p h / 0 5 1 0 2 1 0 v 1 7 O c t 2 0 0 5 Astronomy Astrophysics manuscript no. (will be inserted by hand later) Large scale correlations in galaxy clustering from the Two degree Field Galaxy Redshift Survey N. L. Vasilyev1, Yu. V. Baryshev1, and F. Sylos Labini2,3 1 Institute of Astronomy, St.Petersburg State University, Staryj Peterhoff, 198504, St.Petersburg, Russia 2 “Enrico Fermi Center”, Via Panisperna 89 A, Compendio del Viminale, 00184 Rome, Italy 3 “Istituto dei Sistemi Complessi” CNR, Via dei Taurini 19, 00185 Rome, Italy Received / Accepted Abstract. We study galaxy correlations from samples extracted from the 2dFGRS final release. Statistical prop- erties are characterized by studying the nearest neighbor probability density, the conditional density and the reduced two-point correlation function. The result is that the conditional density has a power-law behavior in redshift space described by an exponent γ = 0.8 ± 0.2 in the interval from about 1 Mpc/h, the average distance between nearest galaxies, up to about 40 Mpc/h, corresponding to radius of the largest sphere contained in the samples. These results are consistent with other studies of the conditional density and are useful to clarify the subtle role of finite-size effects on the determination of the two-point correlation function in redshift and real space. Key words. Cosmology: observations; large-scale structure of Universe; 1. Introduction The problem of the quantitative characterization of the large scale galaxy clustering has been intensively discussed in the last years, especially in relation to two new galaxy surveys: the Sloan Digital Sky Survey (SDSS — York et al., 2000) and the Two degree Field Galaxy Redshift Survey (2dFGRS — Colless et al., 2003). These data rep- resent a great improvement for our knowledge of the local universe: for example the number of measured redshifts has grown of a factor ten with respect to the surveys com- pleted in the last two de