We report on the measurement of the two-point correlation function and the pairwise peculiar velocity of galaxies in the IRAS PSCz survey .
We compute these statistics first in redshift space , and then obtain the projected functions which have simple relations to the real-space correlation functions on the basis of the method developed earlier in analyzing the Las Campanas Redshift Survey ( LCRS ) by Jing , Mo , & Börner ( 1998 ) .
We find that the real space two-point correlation function can be fitted to a power law \xi ( r ) = ( r _ { 0 } / r ) ^ { \gamma } with \gamma = 1.69 and r _ { 0 } = 3.70 h ^ { -1 } { Mpc } .
The pairwise peculiar velocity dispersion \sigma _ { 12 } ( r _ { p } ) is close to 400 { { km s ^ { -1 } } } at r _ { p } = 3 h ^ { -1 } { Mpc } and decreases to about 150 { { km s ^ { -1 } } } at r _ { p } \approx 0.2 h ^ { -1 } { Mpc } .
These values are significantly lower than those obtained from the LCRS .

In order to understand the implications of those measurements on the galaxy biasing , we construct mock samples for a low density spatially-flat cold dark matter model ( \Omega _ { 0 } = 0.3 , \lambda _ { 0 } = 0.7 , \Gamma = 0.2 , \sigma _ { 8 } = 1 ) using a set of high-resolution N-body simulations in a boxsize of 100 h ^ { -1 } Mpc , 300 h ^ { -1 } Mpc , and 800 h ^ { -1 } Mpc .
Applying a stronger cluster-underweight biasing ( \propto M ^ { -0.25 } ) than for the LCRS ( \propto M ^ { -0.08 } ) , we are able to reproduce these observational data , except for the strong decrease of the pairwise peculiar velocity at small separations .
This is qualitatively ascribed to the different morphological mixture of galaxies in the two catalogues .
Disk-dominated galaxy samples drawn from the theoretically constructed GIF catalog yield results rather similar to our mock samples with the simple cluster-underweight biasing .
We further apply the phenomenological biasing model in our N-body mock samples which takes account of the density-morphology relation of galaxies in clusters .
The model does not reduce the velocity dispersions of galaxies to the level measured in the PSCz data either .
Thus we conclude that the peculiar velocity dispersions of the PSCz galaxies require a biasing model which substantially reduces the peculiar velocity dispersion on small scales relative to their spatial clustering .