Université de GenèveDépartement de Physique ThéoriqueCAP Genève

Measuring nonlocal Lagrangian peak bias factors

8. October 2013
Cite as: 
Matteo Biagetti, Kwan Chuen Chan, Vincent Desjacques, Aseem Paranjape [arXiv:1310.1401]

In the Lagrangian approach to halo clustering, nonlocal bias can be generated either
in the initial conditions or by the subsequent gravitational motions. Here, we investi-
gate nonlocal Lagrangian bias contributions involving gradients of the linear density
eld, for which we have predictions from the excursion set peak formalism. We refor-
mulate this approach in order to explicitly take into account the variable describing
the crossing of the collapse barrier. This enables us to write down a bias expansion
which includes all the bias terms, including the nonlocal ones. Having checked that
the model furnishes a reasonable t to the halo mass function, we extend the 1-point
cross-correlation technique of Musso, Paranjape & Sheth (2012) to bias contributions
that are chi-squared distributed. We validate the method with numerical realizations
of peaks of Gaussian random elds before applying it to N-body simulations. We focus
on the lowest (quadratic) order nonlocal bias factors predicted by the excursion set
peaks approach. While the measurements are qualitatively consistent with the theo-
retical predictions, they point to the need for a rened description of the Lagrangian
patches that collapse into haloes.


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