0000000000139818
AUTHOR
Hugh M. P. Couchman
A New Numerical Approach to Estimate the Sunyaev–Zel’dovich Effect
Several years ago, we designed a particular ray tracing method. Combined with a Hydra parallel code (without baryons), it may compute some CMB anisotropies: weak lensing (WL) and Rees–Sciama (RS) effects. Only dark matter is fully necessary to estimate these effects. For very small angular scales, we made an exhaustive study leading to a lensing contribution slightly—but significantly—greater than previous ones. Afterwards, the same ray tracing procedure was included in a parallel Hydra code with baryons. The resulting code was then tested. This code is being currently applied to the study of the thermal and kinetic Sunyaev–Zel’dovich (SZ) contributions to the CMB anisotropies. We present h…
ESTIMATING SMALL ANGULAR SCALE COSMIC MICROWAVE BACKGROUND ANISOTROPY WITH HIGH-RESOLUTIONN-BODY SIMULATIONS: WEAK LENSING
We estimate the impact of weak lensing by strongly nonlinear cosmological structures on the cosmic microwave background. Accurate calculation of large l multipoles requires N-body simulations and ray-tracing schemes with both high spatial and temporal resolution. To this end, we have developed a new code that combines a gravitational Adaptive Particle-Particle, Particle-Mesh solver with a weak-lensing evaluation routine. The lensing deviations are evaluated while structure evolves during the simulation so that all evolution steps—rather than just a few outputs—are used in the lensing computations. The new code also includes a ray-tracing procedure that avoids periodicity effects in a univer…
Improving on numerical simulations of nonlinear CMB anisotropies
An Adaptative-Particle-Particle-Particle-Mesh code (HYDRA) plus a ray-tracing procedure was used in [1] to perform an exhaustive analysis of the weak lensing anisotropy. Other nonlinear Cosmic Microwave Background anisotropies, such as the Rees-Sciamaand the Sunyaev-Zel.dovicheffects are also being studied by using the same tools. Here we present some advances in our study of these nonlinear anisotropies. The primary advance is due to the use of better simulations with greater particle densities and appropriate softening, although other parameters have also been adjusted to get better estimates. Thus, we improve on a previous paper [2] where the Rees-Sciamaeffect was studied with Particle-M…
On the estimation and detection of the Rees Sciama effect
Maps of the Rees–Sciama (RS) effect are simulated using the parallel N-body code, hydra, and a run-time ray-tracing procedure. A method designed for the analysis of small, square cosmic microwave background (CMB) maps is applied to our RS maps. Each of these techniques has been tested and successfully applied in previous papers. Within a range of angular scales, our estimate of the RS angular power spectrum due to variations in the peculiar gravitational potential on scales smaller than 42/h megaparsecs is shown to be robust. An exhaustive study of the redshifts and spatial scales relevant for the production of RS anisotropy is developed for the first time. Results from this study demonstra…
CMB Anisotropy Computations Using Hydra Gas Code
From FFP6 to FFP11, we presented the advances in our Cosmic Microwave Background (CMB) anisotropy computations using N-body Hydra Codes. For such computations, codes without baryons were used: First sequential versions and afterwards parallel ones. With both of them we computed the weak lensing and the Rees-Sciama contributions to the CMB angular power spectrum. Using our numerical techniques, we reported a lensing effect higher than that estimated in previous papers (for very small angular scales). Our CMB computations require less interpolations and approximations than other approaches. This could explain part of our excess of power in lensing computations. Our higher time and angular res…