1. Deciphering the Ancient Universe with the High-Energy Gamma-Ray Emission from GRBs
X-Rays -> see you at COSPAR in July; also Kawai’s talk this conf.
Susumu Inoue (Kyoto U.) with
R. Salvaterra, T. R. Choudhury
Ferrara, B. Ciardi, R. Schneider
(MNRAS in press, arXiv: )
Yoshiyuki Inoue, M. Kobayashi, T. Totani,
Y. Niino (in prep., Poster 34)
Fermi
CTA

2. The Universe
Ryoanji
龍安寺
~1450?
stars
gas
dark matter
dark energy

3. Cosmic Dark Ages to First Light
Nanzenji
南禅寺
~1600?
Pop III GRBs!
Pop III stars
Pop III.2 stars
primordial perturbations

4. slides from T. R. Choudhury

5. gamma-ray absorption: probe of diffuse radiation fields
g + g → e+ + e- E e
threshold condition: E e (1-cos q )>2 me2c4
s peak ,, =4 me2c4
Costamante et al 03
e.g. TeV + 1eV (IR)
100 GeV + 10 eV (UV)
e.g. probe of local IRB through
gamma absorption in TeV blazars
Extragalactic Background Light
blazar
IACT
VHE
EBL e+ e-
from M. Teshima

6. EBL constraints at z=4.35 Abdo+ 09, Sci. 323, 1688
Fermi/LAT detection of GRB C up to 13 GeV without cutoff

7. cosmic star formation rate
from GRB rate
Kistler+ 09
from HUDF
true star formation rate inc. faint galaxies below current detection limit
may be higher than directly observed

8. cosmic star formation rate vs models
Yoshi Inoue+ in prep.
large uncertainties in SFR at z>6

9. cosmic reionization model
Choudhury & Ferrara 05, 06, Choudhury 09
semi-analytical model with Pop III+II stars+QSOs, radiative+chemical feedback
consistent with large set of high-z observations: WMAP, xHI, HUDF NIR counts, etc.
xHI
WMAP3
LLS
reionization
begins z~15
90% z~8
100% z~6
(WMAP7 OK)
Gphotoion
SFR
Lya
TIGM
HUDF
Lyb

10.  absorption optical depth
SI+ arXiv:
MNRAS, in press
(high UV)
low z model
Kneiske+ 04
(high stellar UV)
~0.4
@z=4.35, E=13.2GeV
(GRB C)
appreciable differences in attenuation between z~5-8 at several GeV
→ unique, important info on evolution of UV IRF below Ly edge
= direct census of cosmic star formation rate (indep. of fesc, C)

11. UV intergalactic radiation field (IRF) at high-z
below Ly edge
above Ly edge
<13.6 eV
>13.6 eV
does not ionize HI, weakly absorbed
reasonably uniform
important for  absorption
ionizes HI, strongly absorbed
highly non-uniform
negligible for  absorption
direct measure of UV emissivity
(indep. of escape fraction,
IGM clumping factor)

12. cosmic star formation rate vs models
Yoshi Inoue+ in prep.
large uncertainties in SFR at z>6

13. galaxy formation model (Mitaka model)
semi-analytical model following halo merger histories
consistent with galaxy properties at z<6
galaxy LF
Kobayashi+ 09

14. galaxy formation+reionization model (work ongoing)
include Pop III at Z<10-4 (Schaerer 02)
Y. Inoue+, in prep., see Poster 34
ionizing photon emissivity
sufficient for z<7
electron scattering optical depth
assuming ionization equil.
sufficient if z>10 SFR ~5x higher

15.  optical depth: comparison
Y. Inoue+, in prep.
large differences in
absorption ~ GeV
-> distinguishable
through CTA obs.

16. detectability of high-z GRBs by CTA
GRB C (z=4.3)
Abdo+ 09
GRB C
at z=30
1min
CTA sensitivity curves
CENSORED
1hr
CTA
GRB C extended emission
~ 10-9 erg/cm2/s at T~1000s
extrapolated to TeV (afterglow IC)
neglecting EBL, detectable to z=30!!
distinguish from intrinsic cutoffs
by variability, z-dependence

17. summary
gamma-ray absorption
= effective probe of high-z diffuse UV radiation
= (most robust?) probe of high-z cosmic star formation rate
may also probe escape fraction in combination w. other data
realistic range of models predict absorption
in the GeV range for z~5-10
observable in GRBs by CTA/AGIS out to z~10 & beyond
(if their spectra extend to >100 GeV and neglecting EBL)
high-energy gamma-rays can make essential contributions
to observational cosmology

18. Ginkakuji
(Silver Pavilion)
銀閣寺
~1700?
???