Non-Gaussian morphology on large scales: Minkowski functionals of the REFLEX cluster catalogue

In order to quantify higher-order correlations of the galaxy cluster distri bution we use a complete family of additive measures which give scale-depen dent morphological information. Minkowski functionals can be expressed anal ytically in terms of integrals of n-point correlation functions. They can b e compared with measured Minkowski functionals of volume limited samples ex tracted from the Reflex survey. We find significant non-Gaussian features i n the large-scale spatial distribution of galaxy clusters. A Gauss-Poisson process can be excluded as a viable model for the distribution of galaxy cl usters at the significance level of 95%.