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

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

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

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

Early reionization (WMAP) Spergel et al Instantaneous reionization:

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

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

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

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

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

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

Convergence of c * =1 model

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

Detection of Reneutralization ? Susa Rikkyo University

GP trough of High-z QSOs Fan et al ＠ z=6 Z=5.80 Z=5.82 Z=5.99 Z=6.28 Becker et al., 2001

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

Cen(2003)

High-z Lyα emitter low-z high-z

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 ?

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

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

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

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.