Radiative Feedback on the formation of

first generation subgalactic objects

Hajime Susa

Rikkyo University

First Generation Objects

Predicted by CDM density Perturbation Theory @10<z<30.

M>10^6 M_sun (Tvir>10^3 K) Cooled by H2 lines and H-Lyα

Cooling Diagram 　 (RO +H2) 　

First Generation Objs.

Large Gals.

Cluster of Gals.

12 3 4 5 6 7 8 9

102 3 4 5 6 7 8 9

100

dwarf Gals ?

vir1+z

Cooling by H2

Cooling by H atom

First Generation Subgalactic Objects

Nishi & Susa 1999

Substructure in Galactic Halo

Moore et al. 1999Cluster Halo

Galactic Halo

M 145 10 8

M 122 10 820 times smaller than expected

Feedback

Cooling diagram of primordial gas & SN disruption

Nishi & Susa （ 1999 ）

Primodial Virialized Gas

Cooling ＋ SN disruption

810 halos

merginally survive 100 SN

M M ¤

100SN

10SN

1SN

Wada & Venkatesan 2003

z=10, 10^8 M_sun

1000 SN/Myr →disruption100 SN/Myr →collapse induced

SN (Simulation)

SN feedback

10^8 M_sun halos @z=10 seems to be difficult to be destroyed soley by SN.

But more simulations are required to assess the effects of SN feedback…

Impacts of UVB on GF

PHOTOIONIZATION Production of electrons : catalysts of H2 formation →

enhance the fraction of H2

Enhance the Compton cooling rate

PHOTODISSOCOATION Dissociation of H2 → No coolant

PHOTOHEATING Keep the gas temperature 104-105 K Photo-evaporation Suppression of SF in gals.

Thoul & Weinberg 1996

Cooling and heating rates

Equilibrium temperature is 104-105K

Dynamics of Galaxies with Tvir < 104 Kare strongly affected.

Photoevaporation

Late Reionization, CDM density perturbation, and Radiative cooling.....

Blown away by photo-evaporation

7

If　Z_reion=6,　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

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 than the parent system.

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

Model of SF

2

4

1 5000 K

3 20

2. 5 10

0

4 0

1ga

f

H

s

f

y

T

cdc

dt 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 5

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

21 0.01 I

21 0.01exp 3(17 ) I z

18

Minimally Required I21

0.1, 1HIy

310 , 5HIy

310 , 1HIy 0.1, 5HIy

2

30

(1 )(1 ) 3

4L

plHIrec

HI L

hyI n z k

y

再結合＝光電離

Typical Result (M=107Msun,Zc=10)

300pc

Maximally Star-forming model

100ML

“ Evaporated ”

810 or

20km/srot

M M

v¤d

d

>95% halos are photo-evaporated.

3

456

6

2

3

456

7

2

3

456

2

3

6 7 8 9

102

Vc=20 km/s

Vc=10 km/s

Vc=5 km/s

Convergence (# of particles and Softening )

172N 152N

132N

142N

172N 152N

132N

142N

Substructure in Galactic Halo

Moore et al. 1999Cluster Halo

Galactic Halo

M 145 10 8

M 122 10 820 times smaller than expected

Kravtsov et al. (2004)

～ 10% of halos with 10^8-10^9 M_sun halos are much more massive in the past.

Evidences of invisible substructuresby gravitational lensing

Chiba (2002) Dalal & Kochanek (2002)

Consistent with the CDM N-body simulations

Internal radiative feedback Kitayama, Yoshida, Susa, Umemura 2004 single POPIII star at the center of the cloud

ガスの消失

ガスは失われず

ガスはほぼ完全に消失

ただしガスは星が消えると 10^7 yr くらいかけて戻ってくる。

原始組成からできる星の質量

本当の First Stars → Very Massive ? 再電離を生き残る T_vir ＞ 10^4 K くらいの

雲→ 電離度高 電離度高→ H2 が多量にできる H2 が多量にできると HD が多量にできる⇒

温度が下がって分裂の質量が少し 100Msunよりだいぶ小さくなる (F.Nakamura) 。　

水素分子の過剰生成

衝撃波の後面で再結合の遅れ

およそ 50km/s 以上の衝撃波では水素分子量が a few ×10^{-3} 程度

数万度以上のビリアル温度を持つ雲ではこの過程が起きる。

Susa et al. 1998

Fragment massNakamura & Umemura 2002

Summary 3D RHD の方法で早期再電離のモデルの計算を

行った。 20km/s 以下のビリアル温度を持つ天体の形成は、

早期再電離モデルでは著しく阻害される。 内部の POPIII 星からの radiative feedback の影

響も大きく、 10^7Msun 以下の天体は電離による加熱でガスを失う。

したがって星団としての銀河が誕生するのはビリアル温度が 10^4K 以上の天体と考えられるが、それらの天体ではたとえメタルがほとんどなくても星の質量は少し下がる可能性がある。