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

2. 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 K
Photo-evaporation
Suppression of SF in gals.

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

4. 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

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

6. 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

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

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

9. 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

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

11. 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

12. Model of SF

13. 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.

14. 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

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

16. Minimal I21

17. 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

18. 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.