Linear redshift distortions: A review

Abstract. Redshift maps of galaxies in the Universe are distorted by the peculiar velocities of galaxies along the line of sight. The amplitude of the distortions on large, linear scales yields a measurement of the linear redshift distortion parameter, which is β ≈ Ω0.6 0 /b in standard cosmology with cosmological density Ω0 and light-to-mass bias b. All measurements of β from linear redshift distortions published up to mid 1997 are reviewed. The average and standard deviation of the reported values is βoptical = 0.52 ± 0.26 for optically selected galaxies, and βIRAS = 0.77 ± 0.22 for IRAS selected galaxies. The implied relative bias is boptical/bIRAS ≈ 1.5. If optical galaxies are unbiased, then Ω0 = 0.33 +0.32 −0.22 are unbiased, then Ω0 = 0.63 +0.3