Skewness as a Test of Non-Gaussian Primordial Density Fluctuations

We investigate the evolution of the skewness of the distribution of density fluctuations in CDM models with both Gaussian and non-Gaussian initial fluctuations. We show that the skewness of galaxy counts is a potentially powerful test of the hypothesis of Gaussian primordial density fluctuations. We find, as expected, that the skewness of the mass distribution in models with initially non-Gaussian fluctuations shows systematic departures from the corresponding behaviour for Gaussian fluctuations on intermediate to large scales. We investigate the effect of peculiar velocity distortions and normalization upon the relationship between skewness and variance. These effects are generally small for the models we consider. Comparing our results to the QDOT measurements of the skewness, we find that our initially positive-skew models are clearly excluded by this analysis, but the available data do not rule out the negative-skew models.