Multifrequency analysis of cosmic microwave background radiation and radiation transport in simulations of reionization

Mathematics – Logic

Scientific paper

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Multifrequency, Cosmic Microwave Background Radiation, Radiation Transport, Reionization

Scientific paper

We explore two means for probing cosmology, through multifrequency microwave background measurements and through future observations of the epoch of reionization.
We use multi-frequency information in first year Wilkinson Microwave Anisotropy Probe (WMAP) data to search for the Sunyaev-Zel'dovich (SZ) effect. We derive an optimal combination of WMAP cross-spectra to extract SZ, limiting the SZ contribution to less than 2% (95% c.l.) at the first acoustic peak in W band. Under the assumption that the removed radio point sources are not correlated with SZ, this limit implies s 8 < 1.07 at 95% c.l.
The next generation of microwave telescopes will study the sky at high resolution, scales where both primary and secondary anisotropies are important. We focus on the Atacama Cosmology Telescope (ACT), simulating observations in three channels, and extracting power spectra in a multifrequency analysis. We find that both radio and infrared extragalactic point sources are important contaminants, but can be effectively removed given three (or more) channels and a good understanding of their frequency dependence. However, improper treatment of the scatter in the point source frequency dependence introduces a large systematic bias. The kinetic SZ effect corrupts measurements of the primordial slope and amplitude on small scales. We discuss the non-Gaussianity of the one- point probability distribution function as a way to constrain the kinetic SZ effect, developing a method for distinguishing this effect. We explore the simulation of maps for ACT, their application to the ACT survey geometry, and filtering techniques to recover signals.
Recent work suggests that cosmological fluctuations in reionization developon scales of tens or hundreds of comoving megaparsecs.We build models of ionizing sources from simulations, concluding that a large-scale simulation will require radiation transport from a large fraction of the grid cells. Simulations at a reasonable resolution will have optically thick cells. We extend the work of Cen (2002) to build a parallel radiation transport algorithm which conserves photon flux to a few percent, works well with optically thick cells, and is insensitive to the number of sources in the simulation box.

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