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

Impacts of UVB on GF PHOTO IONIZATION PHOTO DISSOCOATION PHOTO HEATING 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.

Cooling and heating rates Equilibrium temperature is 104-105K Dynamics of Galaxies with Tvir < 104 K are strongly affected. Thoul & Weinberg 1996

SF in cold HI phase ---- Importance of RT and H2cooling ---- Young & Lo 1996, 1997 Leo A , Sag DIG : current SF, two phase LGS 3 : no SF, no cold HI They suggest that existence of cold HI phase is a good indicator of SF. Cooling below 104 K and self-shielding against UVB H2 cooling & Radiation Transfer

Runs in previous work Initial Condition by GRAFIC in COSMICS + Rigid rotation with λ=0.05 Zreion ～ ７

Photo-evaporation → LG dSph? Dark dSphs have large M/L (Mateo 1998)。→ evaporation of gas Spheroidal system →merging of peaks Most of the LG dwarfs have extended old population ( age > 10 Gyrs) (Mateo 1998)。→ Cut-off of SFR

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

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

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

Early Reionization, CDM density perturbation, and Radiative cooling..... Previous runs This work Shaded ≒ Blown away by photo-evaporation 7 20

Method (RSPH) SPH Gravity Radiation transfer of ionizing photons 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

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

Determination of I21at high-z: Lyα Continuum Depression Numerical simulations Confrontation with observations Nakamoto, Umemura & Susa (2001), Hiroi, Umemura Nakamoto in prep. Evolution of IUV：　 I211 at z=3, I210.1 at z=4, I210.01 at z=5

GP trough of High-z QSOs Fan et al. 2002

Minimal I21

Results Photo-evaporation works very well for z_c<15 and M<107M_sun. For M～108M_sun, the photo-evaporation redshift is as large as z_c=8-9

Summary Formation of low mass galaxies are investigated by 3D RHD simulations　with early reionization model. We find zones of photo-evaporated galaxies and large M/L galaxies. But we need more simulations. RT effect is important for the formation of large M/L galaxies CDM substructure problem might be resolved solely by the early reionization model at dSph scale. But we need more detailed analysis. We need statistical analysis in order to discuss the M/L peak of LG dSphs.