Light-Cone Effect on Higher Order Clustering in Redshift Surveys

We have evaluated a systematic effect on counts-in-cells analysis of deep, wide-field galaxy catalogs induced by the evolution of clustering within the survey volume. A multiplicative correction factor is explicitly presented, which can be applied after the higher order correlation functions have been extracted in the usual way, without taking into account the evolution. The general theory of this effect combined with the Ansatz describing the nonlinear evolution of clustering in simulations enables us to estimate the magnitude of the correction factor in different cosmologies. In a series of numerical calculations assuming an array of cold dark matter models, it is found that, as long as galaxies are unbiased tracers of underlying density field, the effect is relatively small (≃10%) for the shallow surveys (z<0.2), while it becomes significant (of order unity) in deep surveys (z~1). Depending on the scales of interest, the required correction is comparable to or smaller than the expected errors of ongoing wide-field galaxy surveys such as the Sloan Digital Sky Survey and the 2 Degree Field Survey. Therefore, at present, the effect has to be taken into account for high-precision measurements at very small scales only, while in future deep surveys it amounts to a significant correction.