The Clustering of Iras Galaxies

We investigate the clustering of galaxies in the QDOT redshift survey of IRAS galaxies. We find that the two-point correlation function is well approximated by a powerlaw of slope −1.11±0.09, with clustering length 3.87±0.32h−1 Mpc* out to pair separations of ∼ 25h Mpc. On scales larger than ∼ 40h Mpc, the correlation function is consistent with zero. The rms fluctuation in the count of QDOT galaxies above the Poisson level in spheres of radius 8h Mpc is σ 8 = 0.58 ± 0.14, showing that fluctuations in the distribution of IRAS galaxies on these scales are smaller than those of optical galaxies by a factor of about 0.65, with an uncertainty of ∼ 25%. We find no detectable difference between the correlation functions measured in redshift space and in real space, leading to a 2σ limit of bIRAS/Ω 0.6 > 1.05, where bIRAS is the bias factor for IRAS galaxies and Ω is the cosmological density parameter. The QDOT autocorrelation function calculated in concentric shells increases significantly with shell radius. This difference is more likely due to sampling fluctuations than to an increase of the clustering strength with galaxy luminosity, but the two effects are difficult to disentangle; our data allow at most an increase of ∼ 20% in clustering strength for each decade in luminosity. For separations greater than ∼ 3h Mpc, the cross-correlation function of Abell clusters (with Richness R ≥ 1) and QDOT galaxies is well approximated by a power-law of slope −1.81 ± 0.10, with clustering length 10.10±0.45h−1 Mpc, and no significant signal beyond ∼>50h−1 Mpc. This cross-correlation depends only weakly on cluster richness.