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.

# Nonlocal peak bias factors: Theory vs Simulations

Topics:

Date:

9. October 2013

Occasion:

Galaxy Bias Workshop, ICTP Trieste

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## Address

Département de Physique Théorique

Université de Genève

24, quai Ernest Ansermet

1211 Genève 4

Switzerland

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