Deciphering the Ancient Universe with theHigh-Energy Gamma-Ray Emission from GRBs

FermiCTA

Susumu Inoue (Kyoto U.) withR. Salvaterra, T. R. ChoudhuryA. Ferrara, B. Ciardi, R. Schneider(MNRAS in press, arXiv:0906.2495)

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

X-Rays -> see you at COSPAR in July; also Kawai’s talk this conf.

Ryoanji龍安寺~1450?

gas

dark energy

The Universe

dark matter

stars

primordial perturbations

Cosmic Dark Ages to First Light Nanzenji南禅寺~1600?

Pop III stars

Pop III GRBs!

Pop III.2 stars

slides from T. R. Choudhury

gamma-ray absorption:probe of diffuse radiation fields

+ → e+ + e-

threshold condition: E (1-cos )>2 me2c4

E

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

peak ,, =4 me2c4

e.g. probe of local IRB throughgamma absorption in TeV blazars

Costamante et al 03

e+

e-

EBLVHE

IACTExtragalactic Background Lightblazar

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

Kistler+ 09

true star formation rate inc. faint galaxies below current detection limitmay be higher than directly observed

from GRB rate

from HUDF

cosmic star formation rate vs models

large uncertainties in SFR at z>6

Yoshi Inoue+ in prep.

cosmic reionization modelChoudhury & Ferrara 05, 06, Choudhury 09semi-analytical model with Pop III+II stars+QSOs, radiative+chemical feedback

WMAP3xHI

SFR

HUDF

Ly

Ly

LLS

photoion

TIGM

consistent with large set of high-z observations: WMAP, xHI, HUDF NIR counts, etc.

reionizationbegins z~1590% z~8100% z~6

(WMAP7 OK)

absorption optical depth

(high UV)

low z modelKneiske+ 04(high stellar UV)

~0.4@z=4.35, E=13.2GeV(GRB 080916C)

SI+ arXiv:0906.2495 MNRAS, in press

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-zbelow Ly edge above Ly edge

- does not ionize HI, weakly absorbed- reasonably uniform- important for absorption

- ionizes HI, strongly absorbed- highly non-uniform- negligible for absorption

<13.6 eV >13.6 eV

- direct measure of UV emissivity (indep. of escape fraction, IGM clumping factor)

cosmic star formation rate vs models

large uncertainties in SFR at z>6

Yoshi Inoue+ in prep.

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

galaxy formation+reionization model (work ongoing)Y. Inoue+, in prep., see Poster 34

ionizing photon emissivitysufficient for z<7

electron scattering optical depthassuming ionization equil.sufficient if z>10 SFR ~5x higher

include Pop III at Z<10-4 (Schaerer 02)

optical depth: comparison Y. Inoue+, in prep.

large differences inabsorption ~10-100 GeV-> distinguishablethrough CTA obs.

detectability of high-z GRBs by CTA

GRB 080916C extended emission~ 10-9 erg/cm2/s at T~1000sextrapolated to TeV (afterglow IC)

Abdo+ 09

neglecting EBL, detectable to z=30!!

distinguish from intrinsic cutoffsby variability, z-dependence

GRB 080916C (z=4.3)

1min

1hrCTA

GRB 080916Cat z=30

CTA sensitivity curves

CENSORED

summary

high-energy gamma-rays can make essential contributionsto observational cosmology

gamma-ray absorption= effective probe of high-z diffuse UV radiation= (most robust?) probe of high-z cosmic star formation rate

observable in GRBs by CTA/AGIS out to z~10 & beyond(if their spectra extend to >100 GeV and neglecting EBL)

realistic range of models predict absorptionin the 10-100 GeV range for z~5-10

may also probe escape fraction in combination w. other data

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