Counts-in-cells comparisons of redshift surveys
G. Efstathiou · Monthly Notices of the Royal Astronomical Society · 1995
A statistical technique is presented for comparing galaxy counts in cells in redshift surveys sampling the same volume of space. The technique can be used to recover the variances and covariances in the cell counts. It can be used to derive the relative amplitude of the clustering pattern traced by galaxies of different types, for example optical and infrared-selected galaxies, early- and late-type galaxies, or luminous and faint galaxies. The statistics can also be used to test for systematic errors in galaxy catalogues. We illustrate the technique with two applications. We compare the cell count statistics of the 1.2-Jy and QDOT redshift surveys of IRAS galaxies, and show that, although there are large differences in the variances measured in cells of size ℓ = 30 and 40 h− 1 Mpc,1 the two surveys are compatible with the hypothesis that they sample the same underlying density field. We show that the variances measured from the QDOT survey are extremely sensitive to a small number of galaxies in the region of the Hercules supercluster. We also compare the clustering of optically luminous and faint galaxies in the Stromlo–APM redshift survey and show, within large errors, that there is no firm evidence for any differences in the clustering properties of galaxies with different luminosities on scales ℓ ≳ 10 h− 1 Mpc.