Spatial clustering in the ESO-Sculptor survey: two-point correlation functions by galaxy type at redshifts 0.1–0.5 ^*,**

¹ Institut d'Astrophysique de Paris, UMR 7095 CNRS, Univ. Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France e-mail: lapparen@iap.fr
² Observatoire de la Côte d'Azur, BP 4229, 06304 Nice Cedex 4, France e-mail: Eric.Slezak@oca.eu

Received: 23 January 2007
Accepted: 4 June 2007

Abstract

Context.Galaxy clustering shows segregation effects with galaxy type, color and luminosity, which bring clues on the relationship with the underlying density field.

Aims.We explore these effects among the populations of giant and dwarf galaxies detected in the ESO-Sculptor survey.

Methods.We calculate the spatial two-point auto and cross-correlation functions for the 765 galaxies with 21.5 and 0.1 ≤ ≤ 0.51 and for subsets by spectral type and luminosity.

Results.At separation of 0.3 h^-1 Mpc, pairs of early-type galaxies dominate the clustering over all the other types of pairs. At intermediate scales,  h^-1 Mpc, mixed pairs of dwarf and giant galaxies contribute equally as pairs of giant galaxies, whereas the latter dominate at 10 h^-1 Mpc. Moreover, the correlation functions per galaxy type display the expected transition between the 1-halo and 2-halo regimes in the scenario of hierarchical merging of dark matter halos. The 1-halo component of the early-type galaxies largely outdoes that for the late spiral galaxies, and that for the dwarf galaxies is intermediate between both. In contrast, the 2-halo component of the early-type galaxies and late spiral galaxies are comparable, whereas that for the dwarf galaxies is consistent with null clustering.

Conclusions.We link the clustering segregation of the early-type and late spiral galaxies to their spatial distribution within the underlying dark matter halos. The early-type galaxies are preferentially located near the centers of the most massive halos, whereas late spiral galaxies tend to occupy their outskirts or the centers of less massive halos. This appears to be independent of luminosity for the early-type galaxies, whereas faint late spiral galaxies might reside in less dense regions than their bright analogs. The present analysis also unveils unprecedented results on the contribution from dwarf galaxies: at the scale at which they significantly cluster inside the halos (≤0.3 h^-1 Mpc), they are poorly mixed with the late spiral galaxies, and appear preferentially as satellites of early-type galaxies.