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 catalogues induced by the evolution of clustering within thesurvey volume. A multiplicative correction factor is explicitly presented,which can be applied after the higher order correlation functions have beenextracted in the usual way, without taking into account the evolution. Thegeneral theory of this effect combined with the ansatz describing thenon-linear evolution of clustering in simulations enables us to estimate themagnitude of the correction factor in different cosmologies. In a series ofnumerical calculations assuming an array of cold dark matter models, it isfound that, as long as galaxies are unbiased tracers of underlying densityfield, the effect is relatively small ($ \simeq 10%$) for the shallow surveys($z <0.2$), while it becomes significant (order of unity) in deep surveys ($z\sim1$). Depending on the scales of interest, the required correction iscomparable to or smaller than the expected errors of on-going wide-field galaxysurveys such as the SDSS and 2dF. Therefore at present, the effect has to be taken into account for highprecision measurements at very small scales only, while in future deep surveysit amounts to a significant correction.Comment: 10 pages, LaTeX, 3 figures and 1 table. Minor revision, accepted for publication in The Astrophysical Journal (Letters