Cross Correlations of the Cosmic Infrared Background

The cosmic infrared background (CIB) is a sensitive measure of the star formation history. But this background is overwhelmed by foregrounds, which bias the CIB mean flux and auto correlation measurement severely. Since dominant foregrounds do not correlate with the large scale structure, the cross correlation of CIB with galaxies is free of such foregrounds and presents as an unbiased measure of the star formation history. In such cross correlation measurement, one can utilize all frequency information, instead of being limited to several narrow frequency windows. This allows the measurement of CIB based on integrated intensity, whose theoretical prediction is based on energy conservation, thus is fairly model independent and robust. The redshift information of CIB sources can be directly recovered with the aid of galaxy photometric redshifts. In the far IR region, correlation signal is around 10% at degree scale. Combining FIRAS and SDSS, the cross correlation can be measured with 20% accuracy (statistical and systematics errors) at l ∼ 40. Such measurement would allow the measurement of star formation rate with comparable accuracies to z ∼ 1. Future CIB experiments with 1 resolution are able to measure the star formation rate with 10% accuracy to z ∼ 1.5. Secondary CMB anisotropies arising from the large scale structure correlate with CIB. The correlation strength is about 0.5μK at ∼ 10 (the integrated Sachs-Wolfe effect) and ∼ −0.3μK at ∼ 1 (the Sunyaev Zeldovich effect, RayleighJeans regime). FIRAS+WMAP would allow the measurement of the ISW effect with & 5σ confidence. Its detection helps to constrain the amount of dark energy and far IR emissivity bias. A future CIB experiment with better angular resolution would allow the measurement of CIB-SZ cross correlation and help to understand the effect of SN feedback on the SZ effect. Subject headings: cosmology: large scale structure; infrared: theory–diffuse background; star: formation