Effects of early reionization on the formation of

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

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

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

SF in cold HI phase ---- Importance of RT and H 2 cooling ---- 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 H 2 cooling & Radiation Transfer

Runs in previous work Initial Condition by GRAFIC in COSMICS + Rigid rotation with λ=0. 05 Zreion ～ ７

Photo-evaporation → LG d. Sph? u Dark d. Sphs have large M/L (Mateo 1998)。 → evaporation of gas u Spheroidal system →merging of peaks u 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 Galactic Halo Moore et al. 1999 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) u SPH • Steinmetz & Muller 1993 • Umemura 1993 u Gravity • HMCS in University of Tsukuba (CCP) • GRAPE 6, direct-sum u Radiation transfer of ionizing photons • Kessel-Dynet & Burkurt 2000 • Nakamoto, Umemura & Susa 2001 u Primordial chemistry & Cooling • Susa & Kitayama 2000 • Galli & Palla 1998

Model of SF

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.

Determination of I 21 at high-z: Lyα Continuum Depression Numerical simulations Confrontation with observations Nakamoto, Umemura & Susa (2001), Hiroi, Umemura Nakamoto in prep. Evolution of IUV： I 21 1 at z=3, I 21 0. 1 at z=4, I 21 0. 01 at z=5

GP trough of High-z QSOs ＠ z=6、α＝５ Fan et al. 2002

Minimal I 21

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

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