We re-examine the gravitational acceleration ( dipole ) induced on the Local Group of galaxies by the Infrared Astronomical Satellite ( IRAS ) galaxy distribution of the Point Source Catalogue redshift survey ( PSCz ) .
We treat the cirrus-affected low galactic latitudes by utilizing a spherical harmonic expansion of the galaxy surface density field up to the octapole order .
We find strong indications for significant contributions to the Local Group motion from depths up to \sim 185 h ^ { -1 } Mpc and possible contribution even from \sim 210 h ^ { -1 } Mpc , in agreement with the recent analysis of Kocevski & Ebeling of a whole sky X-ray cluster survey .
What changes with respect to the previous PSCz dipole analyses is : ( a ) the large-scale dipole contributions and ( b ) an increase of the overall dipole amplitude due to the important contribution of the local volume ( \raise - 2.0 pt \hbox { \hbox to 0.0 pt { \hbox { $ \sim$ } } \raise 5.0 pt \hbox { $ < $ } } 4 h ^ { % -1 } Mpc ) , which we now take into account .
This results in a lower value of the \beta ( \equiv \Omega _ { m } ^ { 0.6 } / b ) parameter , which we find to be \beta _ { IRAS } \simeq 0.49 in real space .
Therefore , for the concordance cosmological model ( \Omega _ { m } = 1 - \Omega _ { \Lambda } = 0.3 ) the IRAS galaxies bias factor is b _ { IRAS } \simeq 1 which means that IRAS galaxies are good traces of the underlying matter distribution .

Keywords : galaxies : clusters : general - large-scale structure of universe - infrared : galaxies