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Early Reionization Impacts on Galaxy Formation: Photo-ionization Mechanisms

Explore the effects of early reionization on galaxy formation with a focus on photo-ionization mechanisms. Study the impacts of ionizing photons on electron production, H2 formation, and momentum transfer in galaxies. Investigate the suppression of star formation through photo-evaporation and photo-heating processes. Understand the role of radiative cooling and density perturbations in the formation of galaxies, sub-clumps, and halo clusters. Utilize simulation models and advanced techniques to analyze the reionization history and detect reneutralization events. Examine the emission profiles and detectability of Lyα and Hα line emissions to probe the reionization history at high redshifts. Discuss the implications of a double reionization scenario on the observable characteristics of galaxies in the evolving universe.

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Early Reionization Impacts on Galaxy Formation: Photo-ionization Mechanisms

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  1. Effects of early reionization on the formation of galaxies Hajime Susa Rikkyo University

  2. Impacts of UVB on GF • PHOTO IONIZATION • Production of electrons : catalysts of H2 formation → enhance the fraction of H2 • Momentum Transfer • PHOTO DISSOCOATION • Dissociation of H2 → No coolant • PHOTO HEATING • Keep the gas temperature 104-105 K • Photo-evaporation • Suppression of SF in gals.

  3. Substructure in Galactic Halo Cluster Halo Moore et al. 1999 Galactic Halo 20 times smaller than expected

  4. Blown away by photo-evaporation Late Reionization, CDM density perturbation, and Radiative cooling..... If Z_reion=7, 1σ density perturbations are not prevented from forming stars. 20 7

  5. Early reionization (WMAP) Spergel et al. 2003 Instantaneous reionization:

  6. Shaded ≒ Blown away by photo-evaporation Early Reionization, CDM density perturbation, and Radiative cooling..... If Z_reion=20, >2σ density perturbations are prevented from forming stars. 20 7

  7. Smaller scale sub-clumps In hierarchical clustering scenario, small clumps evolve faster than the parent system.

  8. Method (RSPH) • SPH • Steinmetz & Muller 1993 • Umemura 1993 • Gravity • HMCS in University of Tsukuba(CCP) • GRAPE6, direct-sum • Radiation transfer of ionizing photons • Kessel-Dynet & Burkurt 2000 • Nakamoto, Umemura & Susa 2001 • Primordial chemistry & Cooling • Susa & Kitayama 2000 • Galli & Palla 1998

  9. Model of SF In order to evaluate the case of maximal star formation rate, we assume

  10. Model of UVB Early Reionization model Put a source outside the simulation box so that the mean intensity is equal to above value at the center.

  11. Maximally Star-forming model (c*=1) “ Evaporated ” >95% halos are photo-evaporated.

  12. Convergence of c*=1 model

  13. Summary 1 • Formation of low mass galaxies are investigated by 3D RHD simulationswith early reionization model. • CDM substructure problem isresolved solely by the early reionization model at dSph scale (<10^8 Msun or Vrot < 20 km/s).

  14. Detection of Reneutralization ? Susa Rikkyo University

  15. GP trough of High-z QSOs Z=5.80 ＠ z=6 Z=5.82 z>7 ... No flux.... Z=5.99 Z=6.28 Fan et al. 2002 Becker et al., 2001

  16. Top Heavy IMF？ +First Stars TOP Heavy Volume fraction of HII region POPII、 Salpeter IMF τe Sokasian et al 2003

  17. Cen(2003)

  18. High-z Lyα emitter low-z high-z

  19. High-z Lyαemitter 2 Haiman 2002 Broad line emission + high SFR ⇒ large self HII region⇒ Still detectable even at neutral universe. How they look like in double reionization universe ?

  20. A double reionization history Ｚ＜６ yh1=0.0001 ６＜ｚ＜９ yh1=0.3 ９＜ｚ＜１９ yh1=0.0001 Ｚ＞１９ yh1=1 Cen like Effects of self-HII region is also taken into account. Haiman like

  21. Emission profile Δv=10km/s, SFR=1Msun/yr Z=15 Z=4 ionized ionized revival Z=23 neutral Z=9 neutral

  22. Flux of Lyα、Hα Detectable by next generation facilities ………….

  23. Summary 2 • It is possible to use F(Lyα)/F(Hα) ratio to probe the reionization history at z > 7. • If double reionization history is assumed, the ratio has characteristic behavior.

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