Intensity Mapping of Molecular Gas During Cosmic Reionization

I present a simple calculation of the expected mean CO brightness temperature from the large-scale distribution of during cosmic reionization. The calculation is based on the cosmic star formation rate density required reionize, and keep ionized, the intergalactic medium, and uses standard relationships between star formation , IR luminosity, and CO luminosity derived for star-forming galaxies over a wide range in redshift. I find the mean CO brightness temperature resulting from the galaxies that could reionize the universe at z = 8 is _B ∼ 1.1(C/5)(fesc/0.1)−1μK, where fesc is the escape fraction of ionizing photons from the first galaxies and C is IGM clumping factor. Intensity mapping of the CO emission from the large-scale structure of the star-forming during cosmic reionization on scales of order 102 to 103 deg^2, in combination with H i 21 cm imaging of neutral IGM, will provide a comprehensive study of the earliest epoch of galaxy formation.