A comparison of the PSCz and Stromlo–APM redshift surveys.

We present a direct comparison of the clustering properties of two redshift surveys covering a common volume of space: the recently completed IRAS Point Source Catalogue redshift survey (PSCz) containing 14 500 galaxies with a limiting flux of 0.6 Jy at 60 μm, and the optical Stromlo–APM survey containing 1787 galaxies in a region of 4300 deg[sup 2] in the south Galactic cap. We use three methods to compare the clustering properties: the counts-in-cells comparison of Efstathiou, the two-point cross-correlation function, and the Tegmark ‘null-buster’ test. We find that the Stromlo variances are systematically higher than those of PSCz, as expected owing to the deficit of early-type galaxies in IRAS samples. However, we find that the differences between the cell counts are consistent with a linear bias between the two surveys, with a relative bias parameter b[sub rel]≡b[sub Stromlo]b[sub PSCz]≈1.3, which appears approximately scale-independent. The correlation coefficient R between optical and IRAS densities on scales ∼20 h[sup -1] Mpc is R⩾0.72 at 95 per cent confidence limit, placing limits on types of ‘stochastic bias’ that affect optical and IRAS galaxies differently. [ABSTRACT FROM AUTHOR]