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:0906.2495) Yoshiyuki Inoue, M. Kobayashi, T. Totani, Y. Niino (in prep., Poster 34) Fermi CTA

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

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

slides from T. R. Choudhury

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

EBL constraints at z=4.35 Abdo+ 09, Sci. 323, 1688 Fermi/LAT detection of GRB 080916C up to 13 GeV without cutoff

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

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

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

 absorption optical depth SI+ arXiv:0906.2495 MNRAS, in press (high UV) low z model Kneiske+ 04 (high stellar UV) ~0.4 @z=4.35, E=13.2GeV (GRB 080916C) 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)

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)

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

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

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

 optical depth: comparison Y. Inoue+, in prep. large differences in absorption ~10-100 GeV -> distinguishable through CTA obs.

detectability of high-z GRBs by CTA GRB 080916C (z=4.3) Abdo+ 09 GRB 080916C at z=30 1min CTA sensitivity curves CENSORED 1hr CTA GRB 080916C 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

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 10-100 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

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