TESTING THE PECULIAR VELOCITY-FIELD PREDICTED FROM REDSHIFT SURVEYS

The reconstruction of the peculiar velocity field from the 1.936-Jy IRAS-selected sample of galaxies is compared with a similar reconstruction from an optically selected sample. A general method for combining different samples to reconstruct a self-consistent density and peculiar velocity field is presented. The method is applied to determine how sensitive the derived peculiar velocity field is to the characteristics of the sample used. The possibility that the IRAS galaxies do not trace the general galaxy population is explored, adopting a simple model of linear biasing between the IRAS and optical samples. We find that the velocity fields derived from the two samples are consistent, within the estimated shot-noise error, for the case of no relative bias. This result suggests that the predicted peculiar velocity field based on IRAS samples is not sensitive to the sampling properties of IRAS galaxies. Combined with a previous suggestion of a relative biasing of IRAS galaxies on small scales (about 5 h-1 Mpc), this result suggests scale-dependent biasing.