Redshift Distortions and Omega in IRAS Surveys

Redshift space distortions on large scales can be used to measure the linear growth rate parameter $\text{ff}\approx {\mathrm{\Omega }}^{0.6}\mathrm{/}b$. I report here measurements of such distortions in the IRAS 2 Jy, 1.2 Jy, and QDOT redshift surveys, finding $\text{ff}=0.69_{-.19}^{+.21}$ from a merged QDOT plus 1.2 Jy catalogue. Unfortunately, confidence in this result is undermined by a marked ($4\sigma$) change in the pattern of clustering in QDOT beyond about $80h^{-1}Mpc$. A similar effect may be present at a mild level in the 1.2 Jy survey. The effect may be caused by systematic variation in the effective flux limit of the IRAS PSC over the sky, with a dispersion of $\sim 0.1$ Jy on scales $\sim 7^{\circ}$\mathrm{.}Ifso,thenthevalueof$\ff$ inferred from redshift distortions in IRAS surveys may be systematically underestimated.