The supergalactic plane revisited with the Optical Redshift Survey

We re-examine the existence and extent of the planar structure in the local galaxy density field, the so-called supergalactic plane (SGP). This struct ure is studied here in three dimensions using both the new Optical Redshift Survey (ORS) and the IRAS 1.2-Jy redshift survey. The density contrast in a slab of thickness 20 h(-1) Mpc and diameter 80 Mpc aligned with the stand ard de Vaucouleurs supergalactic coordinates is delta(sgp)similar to 0.5 fo r both ORS and IRAS. The structure of the SGP is not well described by a ho mogeneous ellipsoid, although it does appear to be a flattened structure, w hich we quantify by calculating the moment of inertia tensor of the density field. The directions of the principal axes vary with radius, but the mino r axis remains within theta(z)similar to 30 degrees of the standard SGP Z-a xis, out to a radius of 80 h(-1) Mpc, for both ORS and IRAS. However, the s tructure changes shape with radius, varying between a flattened pancake and a dumbbell, the latter at a radius of similar to 50 h(-1) Mpc, where the G reat Attractor and Perseus-Pisces superclusters dominate the distribution. This calls to question the connectivity of the 'plane' beyond similar to 40 h(-1) Mpc. The configuration found here can be viewed as part of a web of filaments and sheets, rather than as an isolated pancake-like structure. An optimal minimum variance reconstruction of the density field using Wiener filtering, which corrects for both redshift distortion and shot noise, yiel ds a similar misalignment angle and behaviour of axes. The background-indep endent statistic of axes proposed here can be best used for testing cosmolo gical models by comparison with N-body simulations.