The depth of the multiwavelength data is designed to enable eccurate measurements of photometric redshifts, stellar masses and star formation rates for stellar mass complete (M>M*) samples of galaxies out to z=8, and brighter/more massive galaxies out to z=11.
The wide area covered is respected to result in large statistical samples of the brightest and most massive (M>M*) galaxies in the epoch of reionization, a population which is currently absent in current surveys such as CANDELs due to the relatively small volume probed.
The large area covered and deep multiwavelength data allowing accurate photometric redshift and stellar mass measurements uniquely allows for studying the clustering of galaxies on all relevant physical scales throughout the epoch of reionization, which in turn will provide insight in the co-evolution of galaxies and dark matter haloes during the epoch of initial assembly, as well as both local and global environmental effects on galaxy evolution.
One of the main goals of the Cosmic Dawn Survey is understanding Cosmic Reionization. The first ionized bubbles are expected to form around the most intensely starforming early galaxies. The galaxies are expected to form in the rarest, highest density nodes of the underlying dark matter distribution which from simulations are expected to be degrees apart. The areas covered by current deep extragalactic surveys (e.g. individual CANDELS fields, or the COSMOS field indicated in the figure below) are thus not wide enough to find and characterize the first bubles.
The first reionized bubles are expected to form around z=10, followed by gradual expansion and eventually overlap as the epoch of reionization prooceeds. The brightest galaxies are signposts of the first bubles and will be bright enough to be detected in the Cosmic Dawn Survey.
