Day 665

Monday.

1405.5885
Velocity bias in the distribution of dark matter haloes
Baldauf, Desjacques, Seljak

The standard formalism for the co-evolution of haloes and DM predicts that any initial halo velocity bias rapidly decays to zero.  Argue that, when the purpose is to compute statistics like power spectra etc., the coupling in the momentum conservation equation for the biased tracers must be modified.  New formulation predicts the constancy in time of any statistical halo velocity bias present in the initial conditions, in agreement with peak theory.  Test this prediction by studying the evolution of a conserved halo population in N-body simulations.  Establish that the initial simulated halo density and velocity statistics show distinct fixtures of the peak model and, thus, deviate from the simple local Lagrangian bias.  Demonstrate, for the first time, that the time evolution of their velocity is in tension with the rapid decay expected in the standard approach.

1405.5888
Cosmological constraints from the CFHTLenS shear measurements using a new, accurate and flexible way of predicting nonlinear mass clustering
Angulo, Hilbert

Explore the cosmological constraints from cosmic shear using a new way of modeling the NL matter correlation functions.  The new formalism extends the method of Angulo&White(2010), which manipulates outputs of N-body sims to represent the 3d NL mass distribution in different cosmological scenarios.  Show that predictions from the approach for shear 2-pt correlations at 1 to 300 arcmin separations are accurate at the 10% level, even for extreme changes in cosmology.  For moderate changes, with target cosmologies similar to that preferred by analyses of recent Planck data, the accuracy is close to 5%.  Combine this approach with a MCMC sampler to explore constraints on a LCDM model from the shear correlation functions measured in the CFHTLenS.  Obtain constraints on the parameter combination sigma_8(Omega_m/0.27)^0.6=0.80pm0.3.  Combined with results from CMB data, obtain marginalized constraints on sigma_8=0.81 and Omega_m=0.29.  These results are fully compatible with previous analyses, which supports the validity of the approach.  Discuss the advantages of the method and the potential it offers, including a path to incorporate in detail the effects of baryons, among other effects, in future high-precision cosmological analysis.