Large-Scale Structure from Radio Surveys

Abstract

Radio surveys can be used to probe large-scale structure, >∼ 50 h ^-1 Mpc, in two complementary ways. (1) The observed isotropy of the radio-source distribution places a limit on the largest scale of structure which can be present. Modelling the distribution of galaxies with a Voronoi tessellation, the largest structures consistent with the isotropy of current radio surveys are <∼ 100 h ^-1 Mpc. The strongest constraint is placed by the isotropy of the FIRST survey. (2) Individual structures can be traced efficiently over very large volumes by measuring the redshifts of radio sources from a survey with high space density. Large-scale structure is evident in the spatial distribution of sources in the 5C12 survey (median S _{408 MHZ} ≈ 100 mJy). The much deeper FIRST survey (S _{1.5 GHZ} > 1 mJy) affords an ideal opportunity for tracing filaments, sheets and voids on scales up to ∼ 1000 h ^-1 Mpc.