Review Article

The First Galaxies and the Likely Discovery of Their Fossils in the Local Group

Figure 4

(a) Fraction of baryons retained by each galaxy (normalized to the cosmic mean value, , where ) as function of the halo mass for run S1 in RGS08 at . The size of the dots is proportional to the fraction of stars in each halo: from the largest to the smallest dots we have %, %, % and %, respectively. The plot illustrates the role of internal and external sources of ionizing radiation in reducing the gas retained by small mass halos. Luminous sources (with larger ) retain less gas than dark halos due to winds driven by internal sources of radiation. (b) Average star formation efficiency as a function of halo mass at (left panel) and (right panel) for run S1. We divide all halos into three groups: those at distance  kpc from the nearest luminous halo (solid histograms), those with  kpc (dashed histogram), and those with  kpc (long-dashed histograms). The dot-dashed curve shows the fraction of luminous halos as a function of the halo mass.