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Understanding the Cosmic Infrared Background

Most star formation in the universe took place at high redshift. Hidden from optical observations by shrouds of dust in distant galaxies, it is visible only in the far infrared or in X-rays. Emission from these dusty galaxies constitutes the cosmic infrared background (CIB) which PRISM, owing to its high sensitivity and angular resolution in the far infrared, is uniquely situated to investigate. The survey will sharpen and extend to higher redshifts the determination of the bolometric luminosity function and of clustering properties of star-forming galaxies. Tens of thousands of easily recognizable, bright, strongly lensed galaxies and hundreds of the very rare maximum starburst galaxies, up to z < 6, will be detected, providing unique information on the history of star formation, the physics of the interstellar medium in a variety of conditions up to the most extreme, and the growth of large scale structure, including proto-clusters of star-forming galaxies. The survey will also probe the evolution of radio sources at (sub-)mm wavelengths and provide measurements of the spectral energy distribution (SED) of many thousands of radio sources over a poorly explored, but crucial, frequency range.

Fig 2
The full-sky point source sensitivity of the PRISM polarimetric imager compared to other existing or planned experiments. Each diamond corresponds to the sky-average point source sensitivity (excluding confusion) in a single frequency channel of PRISM . Note that PRISM is in fact confusion limited over the full frequency range, and thus the actual detection limit for both PRISM and SPICA will be similar, slightly higher than the PRISM limit (Figure adapted from Nakagawa, T., et al. 2012, SPIE). For illustrative purposes the SED of the starburst galaxy M82 as redshifted to the values indicated is shown in the background.