Day 1387

Friday.

1803.08185
The Zeldovich approximation and wide-angle redshift-space distortions
Castorina, White

The contribution of the LoS peculiar velocities to the observed redshift of objects breaks the translational symmetry of the underlying theory, modifying the predicted 2pt functions.  These 'wide angle effects' have mostly been studied using linear perturbation theory in the context of the multipoles of the correlation function and power spectrum.  In this work, present the first calculation of wide angle terms in the Zeldovich approximation, which is known to be more accurate than linear theory on scales probed by the next generation of galaxy surveys.  Present the exact result for dark matter and perturbatively biased tracers as well as the small angle expansion of the configuraiton- and Fourier-space 2pt functions and the connection to the multi-frequency angular power spectrum.  Compare different definitions of the LoS direction and discuss how to translate between them.  Show that wide angle terms can reach tens of percent of the total signal in a measurement at low redshift in some approximations, and that a generic feature of wide angle effects is to slightly shift the BAO scale.


1803.08461
Weak lensing peak statistics in the era of large scale cosmological surveys
Fluri, Kacprzak, Sgier, Refregier, Amara

WL peak counts are a powerful statistical tool for constraining cosmological parameters.  So far, this method has been applied only to surveys with relatively small areas, up to several hundred square degrees.  As future surveys will provide WL datasets with size of thousands of square degrees, the demand on the theoretical prediction of the peak statistics will become heightened.  In particular, large simulations of increased cosmological volume are required.  In this work, investigate the possibility of using simulations generated with the fast Comoving-Lagrangian acceleration (COLA) method, coupled to the convergence map generator Ufalcon, for predicting the peak counts.  Examine the systematics introduced by the COLA method by comparing it with a full TreePM code.  Find that for a 2000 deg^2 survey, the systematic error is much smaller than the statistical error.  This suggests that the COLA method is able to generate promising theoretical predictions for WL peaks.  Also examine the constraining power of various configurations of data vectors, exploring the influence of splitting the sample into tomographic bins and combining different smoothing scales.  Find the combination of smoothing scales to have the most constraining power, improving the constraints on the S8 amplitude parameter by at least 40% compared to a single shooting scale, with tomography bringing only limited increase in measurement precision.