The spatial correlation function of IRAS galaxies on small and intermediate scales

Abstract

The spatial correlation function ζ(r) of IRAS galaxies is determined on scales 0.1-30 h-1 Mpc. We use a cross-correlation technique between IRAS galaxies with measured redshifts (and in particular the QDOT survey) and the QMW IRAS galaxy catalogue. This technique has two advantages over traditional estimates: large numbers of galaxies can be used in the analysis, and the results are not affected by the redshift-space distortion that results when redshift catalogues are used alone. We find ζ(r) to be well described by a power law, ζ(r) = (r/r0)-y, with r0 = 3.79±0.14 h-1 Mpc and γ= 1.57 ±0.03. Combining the amplitude of galaxy clustering found here with previous work on the biasing of IRAS galaxies, we derive a value for the rms mass density variation in 8 h-1 Mpc spheres of σ8 = 0.58 ± 0.11. The results presented here are consistent with the clustering and level of biasing on large scales derived from the QDOT redshift survey. They also represent a marginal detection (3σ) that the correlation function of IRAS galaxies is shallower than that of optically selected galaxies. If confirmed, it would explain why IRAS galaxies appear less clustered on small scales but show strong large-scale clustering.