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
Substructure in Galactic Halo
Moore et al. 1999Cluster Halo
Galactic Halo
M 145 10 8
M 122 10 820 times smaller than expected
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
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
Substructure in Galactic Halo
Moore et al. 1999Cluster Halo
Galactic Halo
M 145 10 8
M 122 10 820 times smaller than expected
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
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