Wiener Reconstruction of All-Sky Spherical Harmonic Maps of the Large Scale Structure

Abstract

A statistical method for reconstructing large scale structure behind the Zone of Avoidance is presented. It also corrects for shot-noise and for redshift distortion in galaxy surveys. The galaxy distribution is expanded in an orthogonal set of spherical harmonics. We show that in the framework of Bayesian statistics and Gaussian random fields the $4 π$ harmonics can be recovered and the shot-noise can be suppressed, giving the optimal picture of the underlying density field. The correction factor from observed to reconstructed harmonics turns out to be the well-known Wiener filter (the ratio of signal to signal+noise), which is also derived by requiring minimum variance. We apply the method to the 1.2 Jy IRAS survey. A reconstruction of the projected galaxy distribution confirms the connectivity of the Supergalactic Plane across the Galactic Plane (at Galactic longitude $l \sim 135^o$ and $l \sim 315^o$) and the Puppis cluster behind the Galactic Plane ($ l \sim 240^o$). The method is extended to 3-D, and is used to recover from the 1.2 Jy redshift survey the density, velocity and potential fields in the local universe.