Improved non-Gaussian Mass Functions for Halos and Voids

by Dr marcello Musso (ICTP)

Friday 22 Oct 2010, 11:30 → 12:30 Europe/Zurich

Auditoire 234 (Geneva University)

The abundance of collapsed objects in the Universe, or halo mass function, is an important tool in studying the imprints of primordial non-Gaussianities on large scale structures. Non-Gaussian analytical corrections to the Gaussian result can be computed perturbatively in the framework of the excursion set theory. However, the involved parameters are scale dependent and some become of order unity for large mass scales or at high redshifts, spoiling the validity of the perturbative expansion.
Combining path integral methods and saddle point techniques (separately applied in previous approaches) allows a non-perturbative treatment of the dengerous terms. Hence, an accurate expression for the mass function is obtained, which is valid over a larger range of mass scales and redshifts (also accounting for multi-scale density correlations).
In addition, by tracking the terms neglected in the analysis, the theoretical uncertainties can be estimated, allowing comparisons between different approaches. For this result, the dominant error is due to approximations related to the choice of the smoothing filter function, and not due to the truncation of the expansion in non-Gaussian parameters.
The same technique can also be generalized to study cosmic voids. Some of the arising complications are discussed.