1) First Light: JWST's top science goal is finding the light from the first objects to coalesce after the Universe cooled following the Big Bang (see Fig. 3). The potential of JWST for studying distant sources has prompted a number of theoretical studies predicting the properties of the first stars, which are thought to be quite different from stars forming today because of the lack of any elements heavier than helium.
Ultra-deep imaging and spectroscopic surveys using JWST are expected to detect the first super star clusters, or proto-galactic objects, to form at redshifts as high as z = 15-20. Appropriate timing of the observations may enable the detection of individual supernovae of super-massive population III stars. These surveys, along with spectroscopy of the highest redshift quasars, will trace the evolution of the first light objects through the epoch of reionization.
2) Assembly of Galaxies: The same observational drivers that define the search for first light also support detailed study galaxy assembly. Specifically, how do galaxies evolve from small, sub-galaxy sized fragments into the suite of morphologies and galaxy types (the Hubble Sequence) that we see today? For example, there is a significant body of literature describing how smaller mass condensations might hierarchically cluster (and evolve) to build clusters of galaxies, and eventually individual galaxies that we see today (see Fig. 4). Areas requiring additional work include the details of how the mass condensations predicted by Cold Dark Matter (CDM) models form stars and become luminous. This, of course, relates to the first light theme, although the full history of star formation is of interest from the perspective of the assembly of galaxies.
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