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Session 87 - Large Scale Structure.
Display session, Friday, January 09
Exhibit Hall,
The Microwave Anisotropy Probe (MAP) mission will produce a multi-frequency map of the microwave background at five frequencies (22 GHz - 90 GHz) with a resolution of 0.21 degrees at its highest frequency. While microwave background fluctuations are thought to be generated primarily at the surface of last scatter, there are several low redshift (z < 3) processes that also distort the microwave background. These processes include scattering of microwave photons off of hot gas (Sunyaev-Zeldovich effect); the gravitational lensing of the microwave background; and the generation of additional microwave fluctuations by time-variable gravitational potentials (Rees-Sciama effect and the Integrated Sachs-Wolfe effect). While it will be difficult to detect these effects directly in the microwave maps, they may be detectable by cross-correlating the microwave maps with surveys that probe the large scale structure. Specifically, we consider cross-correlations of the CMB temperature with extragalactic source surveys in the optical (e.g., the future Sloan Digital Sky Survey), and the radio band (e.g., the FIRST survey). In addition, we also consider a cross-correlation with both the discrete and diffuse components of the cosmic X-Ray Background. A cross-correlation signal is expected between these tracers and the CMB fluctuations produced by the Integrated Sachs-Wolfe effect and the Sunyaev-Zel'dovich effect. In addition, we consider weak gravitational lensing as a tracer of the foreground potential. Weak lensing can be measured using the distortions of the apparent shapes of distant galaxies, as well as their number counts.
By detecting these cross-correlations, we can both measure the bias parameter (the ratio of fluctuations in the galaxy counts to fluctuations in the mass distributions) and better understand the extragalactic "foregrounds".
