Effects of early reionization on the formation of galaxies

Hajime SusaRikkyo University

Impacts of UVB on GFPHOTO IONIZATION

Production of electrons : catalysts of H2 formation → enhance the fraction of H2

Momentum Transfer

PHOTO DISSOCOATIONDissociation of H2 → No coolant

PHOTO HEATINGKeep the gas temperature 104-105 KPhoto-evaporationSuppression of SF in gals.

Substructure in Galactic Halo

Moore et al. 1999Cluster Halo

Galactic Halo

M 145 10 8

M 122 10 820 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)

( ) 0.17 0.04recz

Spergel et al. 2003

Instantaneous reionization:

17 3reionz

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

xIn hierarchical clustering scenario, small clumps evolve faster thanthe parent system.

Method (RSPH)SPH

Steinmetz & Muller 1993Umemura 1993

GravityHMCS in University of Tsukuba (CCP)GRAPE6, direct-sum

Radiation transfer of ionizing photonsKessel-Dynet & Burkurt 2000 Nakamoto, Umemura & Susa 2001

Primordial chemistry & CoolingSusa & Kitayama 2000Galli & Palla 1998

Model of SF

2

4

1 5000 K

3 20

2. 5 10

0

4 0

1ga

f

H

s

f

y

T

cd cdt t

***

.

.

.

,

v

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

Model of UVB

3

21 1 / 3 I z

1

21 exp 12 3 I z

1 z

21I

3 5Put a source outside the simulation box so that the mean intensity is equal to above value at the center.

21 0.01 I

21 exp 3(17 ) I z

Early Reionization model

0t 86.5 10 yeart 91.1 10 yeart

91.5 10 yeart 93.5 10 yeart 93.7 10 yeart

93.9 10 yeart 94.9 10 yeart 97.0 10 yeart

2410

2910

2610

2510

2710

2810

-3[g cm ]

Maximally Star-forming model (c*=1)

100ML

“ Evaporated ”

810 or20km/srot

M Mv

¤d d

>95% halos are photo-evaporated.

3

456

106

2

3

456

107

2

3

456

108

2

3

6 7 8 910

2

Vc=20 km/s

Vc=10 km/ s

Vc=5 km/ s

Convergence of c*=1 model

172N 152N

132N

142N

172N 152N

132N

142N

Summary 1Formation 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. 2002

221 120.67 0.013 10HII y

d t

＠ z=6Z=5.80

Z=5.82

Z=5.99

Z=6.28

Becker et al., 2001

Top Heavy IMF ？

Sokasian et al 2003

Volume fractionof HII region

τe

POPII 、Salpeter IMF

+First StarsTOP Heavy

Cen(2003)

High-z Lyα emitter

low-z

high-z

High-z Lyαemitter 2

Haiman 2002Broad 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=0.0001６＜ｚ＜９ yh1=0.3９＜ｚ＜１９ yh1=0.0001Ｚ＞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

1.0

0.8

0.6

0.4

0.2

0.0100500-50

x10- 6

1.0

0.8

0.6

0.4

0.2

0.0100500-50

x10- 6 1.0

0.8

0.6

0.4

0.2

0.0100500-50

x10- 6

1.0

0.8

0.6

0.4

0.2

0.0100500-50

x10-6

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.