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, 𝑀_bar=𝑓^max_bar𝑀_dm, where 𝑓^max_bar=Ω_𝑏/Ω_𝑚=0.136) as function of the halo mass 𝑀_dm for run S1 in RGS08 at 𝑧=10. The size of the dots is proportional to the fraction of stars 𝑓_∗=𝑀_∗/𝑀_bar in each halo: from the largest to the smallest dots we have 𝑓_∗>10%, 1<𝑓_∗<10%, 0.1<𝑓_∗<1% and 𝑓_∗<0.1%, 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 𝑓_∗) retain less gas than dark halos due to winds driven by internal sources of radiation. (b) Average star formation efficiency ⟨𝑓_∗⟩ as a function of halo mass at 𝑧=10.2 (left panel) and 12.5 (right panel) for run S1. We divide all halos into three groups: those at distance 𝑑<8 kpc from the nearest luminous halo (solid histograms), those with 8kpc<𝑑<50 kpc (dashed histogram), and those with 𝑑>50 kpc (long-dashed histograms). The dot-dashed curve shows the fraction of luminous halos 𝐹_lum(𝑀_dm) as a function of the halo mass.

(a)

(b)