高エネルギー天体で探る初代星・銀河形成
GRB + blazar
井上 進（京大理）+共同研究者いろいろ

1. UV background
2. intergalactic magnetic fields
3. very first star (GRB)
4. dustFermi (GLAST)
GeV

z~60-6
GRBblazar

first star epochz~100-10
Pop 3 =metal/dust-free, H2+HD-coolingassume: no metal/dust, CR, B field, turbulence (DM annih.)

Pop 3.1 (1st generation) massive, high UV
1st HIIR (ion.+comp.) -> IGM reionization
1st SN (ion.+comp.) -> 1st metal/dust (+CR+B)

1st BH -> 1st QSO

Pop 3.2 (2nd generation)
not-so-massive?
Pop 2 =metal/dust-cooling
1st sun -> 1st planet, life, human!

観測ほとんど皆無=理論屋の天国
1st gen.はわかったつもり
2nd gen.研究に移行

Yoshida, Omukai & Hernquist 08

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arXiv:0808.0472

dark stars???
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最近多くの人が悪のりして小流行観測が全くないとこんなこともまかりとおる
GRBを使って鉄槌を下すべし

gamma-ray bursts

ultrarelativistic outflow+shocks

adapted from Meszaros 01

prompt X-γ emissioninternal shocks

optical flash, radio flareradio-IR-opt-X afterglow

external reverse shock external forward shockblazars

relativistic jet+internal shocks

GeVTeVblazar sequence
Fossati+ 98

1. gamma-ray absorption:probe of diffuse radiation fields
γ + γ → e+ + eE εthreshold condition: E ε (1-cos θ )>2 me2c4
σ peak,,=4 me2c4

e.g. TeV + 1eV (IR)100 GeV + 10 eV (UV)

Costamante et al 03

probe of local IRB throughgamma absorption in TeV blazars

probing local IR background with gamma-ray absorption
HESS observations of TeV blazars @z=0.165, 0.186
Aharonian+ 06 Nat.

• strongly rules out NIR peak
• little “missing light”

no strong Pop III

gamma-ray absorption at higher z
Albert+ 08 Sci.

Eγ(τ=1)

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MAGIC observation
80-500 GeV
3C279 @z=0.536

まともなblazarのスペクトル（α>1.5）なら銀河カウントからの下限値に近い（missing lightは少ない）

gamma absorption at very high-z (reionization epoch)?
Oh 2001 ApJ 553, 25 (also Madau & Phinney 96)

reionizing radiation fields should induce ~10 GeV absorption
spectral attenuation factor

τ=1 γ-ray energy

low SFRhigh SFR

E (GeV)

pre-WMAP z<10 only, no Pop III- reionizing radiation much better constrained now- z>10, effect of Pop III not well exploredhigh-z UV radiation fields from cosmic reionization model
Choudhury & Ferrara 05, 06
semi-analytic treatment with radiative+chemical feedback parameters ε*II, ε*III, ηesc, λ0IGM
consistent with large set of high-z observations inc. WMAP3, xHI, HUDF NIR counts, etc.
xHI

SFR

HUDF

WMAP3(WMAP5 OK)LLSreionization
begins z~15
90% z~10
100% z~6LyαΓphotoion

LyβTIGMSI, Salvaterra, Choudhury,Ferrara, Schneider, Ciardi
to be submitted

pair absorption optical depth
107654CF06
Kneiske04 (high UV)

3τ(E)

2

1
765468

32

1020

554

3low z (0<z<5) model
Kneiske et al 04(high stellar UV)

2
10.1

5

10

152025 30

E [GeV]significant optical depth from z~5-8 at several GeV
but not much effect z>~8 due to declining star formation, time intervalpair absorption attenuation factor
1.00.820

11080.662exp(-τ(E))

55430.4

low z (0<z<5) model
Kneiske et al 04(high stellar UV)

0.2

CF06
Kneiske04 (high UV)
510E [GeV]

1520GLAST, 5@5appreciable differences in cutoffs between z~5-8 at several GeV→ unique, important info on evolution of UV at reionization epochdifferent reionization models

different Pop III efficiency,IMF, escape fraction, etc.

1.00.8exp(-τ(E))

0.61201086255430.4

more realistic(Gnedin) model ofradiative feedback

0.2

CF06
GnedinKneiske04
510

1520

E [GeV]

only slight differences→ cutoff predictions robust? → useful as redshift indicators?

very high-z blazars: detectability

GLAST (>100 MeV)
source count1yr survey

Y. Inoue, SI+ (?)

appreciable numberat z~6-10!

blazar evolution model (Y. Inoue & Totani, in prep.)- blazar sequence- L-dependent density evolution (cosmic downsizing) up to z~5- EGRET observations
extrapolation to high-z

2. “pair echos” (delayed secondary emission)probe of intergalactic magnetic fields
Plaga 95
sensitive to very weakintergalactic magnetic fields

GRBγ ~TeV
MeVtAeIRe+tB
CMBtICBγ ~GeVCMBγdelay
MeVIchiki, SI, Takahashi
ApJ 682, 127
new formulation
distinguish coherent or random B
dependence on coherence lengthintergalactic magnetic fields in voids
very weak primordial or high-z B fields could have survived“intergalactic archaeology”
BnHI

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z=3z=1z=0.5z=0T

Gnedin+ 00B generation by Biermann battery
at high z reionization fronts
B~10-20-10-18 G

Bertone+ 06

B seeding by Galactic winds
quasar outflows
Furlanetto & Loeb 01

probing intergalactic magnetic fields with “pair echos”
Ichiki, SI, Takahashi
ApJ 682, 127~0.3 Mpc~20 Mpc
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B=10-18 G, lc=100pc
Emax=10 TeV
important difference
for coherent/random fields

GRB pair echos: detectability
Takahashi, Murase, Ichiki, SI+
arXiv:0806.2825
detectable out to z~<0.71 GeV

100 GeVpair echos from TeV blazar flares
Murase, Takahashi, SI, Ichiki+
ApJL in press (arXiv:0806.2829)

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Mrk 501 flare3. The very first “GRB”:
characteristic signatures at z~30-60?

1054 erg/s

1053
1052

peak energy ~10 keV (XRF)
long duration ~1000s

Naoz & Bromberg 07

宇宙の一番星を見つけるには？

high-z GRB afterglows in IR

c.f. SI, Omukai & Ciardi
2007 MNRAS 380, 1715-24

t=1 daylog fν [erg s-1 cm-2 Hz-1]

Ly α-26z=1-28SPICA

510Spitzer

30-30

3 hr integ.
5σ sensi.
-32
12.0

Subaru3h S/N=10 R=100

12.5

13.0

E=1053erg, nCBM=1 cm-3
θj=0.1, εe=0.1, εB=0.01, p=2.2
13.5

14.0

14.5

15.0

15.5log ν [Hz]Subaru (ground) only up to z~17
Ly break >3-7 μm

SPICA, JWSTCompton attenuation

SI, Nakamura+ (?)

concordance universe
Thomson thick at z>~56
τTE>~keV indep. of ionization
E>~MeV Klein-Nishina decline

Compton attenuated spectrumzlog Eγ(τ=1)

gamma absorption by high-z CMB?

z4. first dust

Pop 3 → Pop 2 transition

collapsing zero/low-metal clouds- 1-zone, simplified dynamics- detailed chemistry inc. HD+metals+dust

H2Omukai+ 05 model

T minimum -> fragmentation

dust

H2+HD

[Z/H]<-6: Mfrag~103MΘ Pop 3-3<[Z/H]<-5: Mfrag~0.1-100MΘ Pop 2!

[Z/H]crit=-5+-1

absorption by first dust (optical depth at fragmentation)

implications if observable- probe of Pop 3 → Pop 2 epoch (formation of first sun)!
- absence=Pop 3 signature?
すばるで何かできるかも？
- probe of first dust properties

caveats: dust distribution in GRB environment
dust-cooled fragments -> not GRB progenitors?
effect of progenitor evolution: UV, HII region, wind …
destruction by GRB UV+X
foreground star forming cores
dustGRBrdest

star forming cores triggered byphotodiss. region driven shock
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GRBTsuribe & Omukai 06

まとめ
ガンマ線吸収で再電離UVを探る
z~5-8では数GeV帯域 blazar+GLASTでできる２次ガンマ線(pair echo)で銀河間磁場を探る
z~<0.7 GRB or blazar + GLAST, MAGICでできるかも
宇宙の一番星を探す方法 コンプトン減衰？
もっと検討必要
赤外吸収でダスト（生命、人間の元）を探る
GRB＋SPICAで（すばるでも）できるかもz>10 first star epochは観測未開拓
現在蛮族（理論屋）の支配下
GRB, blazarで切り開く！