Large- and superlarge-scale structure in the Las Campanas redshift survey

In this paper we employ a core-sampling analysis to find characteristic scales for the large- and the superlarge-scale structure (LSS and SLSS, respectively) in the Las Campanas Redshift Survey (LCRS), With this method, we show that the spatial distribution of galaxies can be roughly characterized as a superposition of three different populations of structural elements: the richest and most stable part is composed of sheet-like elements which can be identified with the SLSS; a system of rich filaments forms the stable part of the LSS; and a system of poor, sparsely populated filaments, lying preferentially in underdense regions, completes the LSS construction. The SLSS incorporates about 60 per cent of the galaxies within the full survey sample, and this value changes little for subsamples constrained by absolute magnitude. Hence, the number density of galaxies is heavily modulated by the SLSS. The spatial distribution of the SLSS elements is approximately Poissonian and is characterized by a mean separation of elements D-sc approximate to (77 +/- 9) (h-1) Mpc for the full LCRS sample. This value for D-sc depends only weakly on galaxy luminosity. The stable component of the LSS contains about 20 per cent of the galaxies in the full sample, and the spatial distribution of this component can also be approximated as Poissonian. This distribution is characterized for the full LCRS sample by the mean separation of filaments D-fc approximate to (30 +/- 2) h(-1) Mpc. The poorest and most sparsely populated component of the LSS contains about 20 per cent of the galaxies in the full LCRS sample. The spatial distribution of this component of the structure can also be described as Poissonian and can be characterized by a mean separation of filaments D-fc approximate to (12.9 +/- 0.3) h(-1) Mpc. The projected proper thickness of the sheets, t(pr), is approximate to (4-5) h(-1) Mpc, much smaller than the separation of the sheets themselves; hence, galaxies tend to be confined to a relatively small fraction of the survey volume. This heavy concentration of galaxies within the sheets of SLSS, however, is not necessarily accompanied by a similar concentration of dark matter.