Reionization

Figure 1: Milestones in the evolution of the universe from simplicity to complexity. The “end of the dark ages” bridges between the recombination epoch probed by microwave anisotropy experiments (z 10³) and the horizon of current observations (z 5–6). NGST, New generation space telescope.
Figure 3: Stages in the reionization of hydrogen in the intergalactic medium.

Figure 2: Transmitted flux blueward of Lyα emission as a function of redshift from z2 to 6.3 using Keck/ESI and HIRES data. Large open red squares are points data for possible BAL quasars. Flux was computed in bins of 15 Å.

Figure 3: Evolution of optical depth with combined Lyα and Lyβ results. The dash line is for a redshift evolution of τ_GP (1 + z)^4.3. At z > 5.5, the best-fit evolution has τ_GP (1 > z)^>10.9, indicating an accelerated evolution. The large open symbols with error bars are the average and standard deviation of optical depth at each redshift. The sample variance also increases rapidly with redshift.

Figure 6: Evolution of volume-averaged neutral hydrogen fraction of the IGM. The solid points with error bars are measurements based on the 19 high-redshift quasars. The dashed and dashed-dotted-dashed lines are volume-averaged results from the A4 and A8 simulations of Gnedin (2004). The neutral fraction inferred from the observations is comparable to the transition from overlap stage to postoverlap stage of reionization in simulations (Gnedin 2000).

Figure 15: The volume-averaged neutral fraction of the IGM versus redshift using various techniques. The dashed line shows the fiducial model of Gnedin (2004) with late reionization at z = 6–7 (see also Gnedin & Fan 2006). The solid line shows an idealized model with double reionization as described in Cen (2003a), and the dotted line illustrates the model with early reionization at z14.