First Star Signature in Infrared Background Anisotropies

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  • 22 August 2003
Abstract
Recent cosmic microwave background anisotropy results from the Wilkinson Microwave Anisotropy Probe suggest that the universe was reionized at a redshift around 20 with an optical depth for Thomson-scattering of 0.17 +/- 0.04. Such an early reionization could arise through the ionizing radiation emitted by metal-free population III stars at redshifts of 10 and higher. We discuss infrared background (IRB) surface brightness spatial fluctuations from such a generation of early star formation. We show that the spatial clustering of these stars at tens of arcminute scales generates a contribution to the angular power spectrum of the IRB anisotropies at the same angular scales. This excess can be potentially detected when resolved foreground galaxies out to a redshift of a few is removed from the clustering analysis. Additionally, assuming a population III stellar spectrum, we suggest that the clustering excess related to the first generation of stars can be separated from brightness fluctuations resulting from other foreground sources and galaxies using multifrequency observations in the wavelength range of ~ 1 to 5 \mu m. Using angular power spectra of the IRB anisotropy, we examine the extent to which the spatial fluctuations, and the star formation rate at redshifts between ~ 10 and 30, can be studied with various instruments.

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