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Effects of early reionization on the formation of galaxies

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

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Effects of early reionization on the formation of galaxies

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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. Cooling and heating rates Equilibrium temperature is 104-105K 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. Blown away by photo-evaporation Early Reionization, CDM density perturbation, and Radiative cooling..... If Z_reion=7, 1σ density perturbations are not prevented from forming stars. 20 7

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

  11. 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

  12. Model of SF

  13. 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.

  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 ＠ z=6、α＝５ 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 simulationswith 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 mightbe 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.

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