The 2dF Galaxy Redshift Survey: higher order galaxy correlation functions

We measure moments of the galaxy count probability distribution function in the two-degree field galaxy redshift survey (2dFGRS). The survey is divided into volume limited subsamples in order to examine the dependence of the higher order clustering on galaxy luminosity. We demonstrate the hierarchical scaling of the averaged p-point galaxy correlation functions, xibar_p, up to p=6. The hierarchical amplitudes, S_p = xibar_p/xibar_2^{p-1}, are approximately independent of the cell radius used to smooth the galaxy distribution on small to medium scales. On larger scales we find the higher order moments can be strongly affected by the presence of rare, massive superstructures in the galaxy distribution. The skewness S_3 has a weak dependence on luminosity, approximated by a linear dependence on log luminosity. We discuss the implications of our results for simple models of linear and non-linear bias that relate the galaxy distribution to the underlying mass.