The abundance of high-redshift objects as a probe of non-Gaussian initial conditions

The observed abundance of high-redshift galaxies and clusters contains prec ious information about the properties of the initial perturbations. We pres ent a method to compute analytically the number density of objects as a fun ction of mass and redshift for a range of physically motivated non-Gaussian models. In these models the non-Gaussianity can be dialed from zero and is assumed to be small. We compute the probability density function for the s moothed dark matter density held, and we extend the Press-Schechter approac h to mildly non-Gaussian density fields. The abundance of high-redshift obj ects can be directly related to the non-Gaussianity parameter and thus to t he physical processes that generated deviations from the Gaussian behavior. Even a skewness parameter of order 0.1 implies a dramatic change in the pr edicted abundance of z greater than or similar to 1 objects. Observations f rom the Next Generation Space Telescope (NGST) and X-ray satellites (XMM) c an be used to accurately measure the amount of non-Gaussianity in the primo rdial density held.