GALACTIC ARCHEOLOGY AND THE HIGH-REDSHIFT DETECTABILITY OF MILKY WAY HALO PROGENITOR GALAXIES

Using a simple model of Milky Way halo formation and chemical evolution, we examine the criteria for observing Milky Way-like progenitor galaxies and the stellar populations within them with the James Webb Space Telescope (JWST). We determine that Milky Way progenitors are visible in deep fields (AB = 30-31) up to z = 7 with low dust content and up to z = 9 with no dust content. These models allow us to determine the fraction of Milky Way halo stars formed in galaxies that should be visible with Near-Infrared Camera on JWST, as a function of metallicity. We show that galaxies in which Galactic halo stars of metallicity above [Fe/H] = -2.5 formed can be detected. Galaxies that form stars with higher metallicities should be visible in deep fields and can be studied by combining observations within the Galaxy as well as external galaxies. We find that halo stars with [Fe/H] < -2.8 formed in progenitor galaxies that are not visible to JWST and that examining their remnants within the Milky Way provides the only realistic prospect of studying these ancient stellar populations. The oldest visible stellar populations are shown to be centrally concentrated, with the stars that formed in visible galaxies at z > 3 residing preferentially within the central 10 kpc region of the Galaxy.