Deciphering the Ancient Universe with Gamma-Ray

BurstsNobuyuki Kawai (Tokyo Tech)

http://www-tap.scphys.kyoto-u.ac.jp/GRB2010/

Cosmic Time

Neutral opaque Universe Ionized

transparent Universe

GRB as a probe for high-z UniverseGRB as a luminous light source

GRB as a mark for a death of a massive star

3

Imprints in GRB spectra

Molecular Cloud

H II Region

WR Wind Shell

SN ejecta

galaxy ISM

IGM

Ejecta CSM SFR ISM IGM

4

Lya break

SII

SiII*OI CII

SiII

GRB 050904 at t=3.4 d

Subaru FOCAS 4.0 hrs, l/Dl»1000Kawai et al. (2006)Totani et al. (2006)

[S/H]=-1.3

Log NHI=21.6

zIGM,u = zDLA = 6.295 best fit xHI = 0.00 xHI < 0.17 (68 %

C.L.) 0.60 (95%

C.L.)

History of the Universe

5

• Reinization• Chemical

evolution• Star formation

rate

IGM

Neu

tral F

ract

ion

Met

allic

ity

Cos

mic

star

form

atio

n ra

te

“Tanvir Plot”

Tanvir 2009

GRBs

Galaxies

Quasars

7

960 970 980 wavelength 　 [nm]

2 1 0 Flux density

Lya

700 800 900 1000 wavelength 　 [nm]

1

0

Lya

S+

Si+Si+

O C+

800 900 1000 wavelength 　 [nm]

30

20

10

0

Lya

optical/NIR spectra of highest-z objectsGalaxyz = 6.96

Quasarz = 6.4

GRBz = 6.3

•Lyman alpha emitter•can be found with

systematic wide-field narrow band survey + spectroscopy•little information in

spectra (e.g. metal?)•luminosity selected

•very rare: only 10 at z>6 in SDSS•steadily bright•complicated

spectra: difficult to interpret•proximity effect•luminosity-

selected

•rare: ~<5% at z>6 ?•bright at early phase•simple intrinsic

spectra: abundant information

•no proximity effect•sampling normal

star-forming glaxy

8

Agenda What do we know about GRBs? What do we know about the

ancient Universe? How can we use GRBs to

understand the history of the Universe?

What are the future prospects?

9

Poster Competition Eligible if you are not giving a

talk Indicate your entry by the color

sticker Entry closed at Monday afternoon

Anonymous Judges choose three winners

Winners give 10 min talk on Friday

Young participants (students, postdocs) are particularly encouraged

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Cosmic Chemical Evolution

Fynbo et al. 2006Prochaska et al. 2003Sollerman et al. 2005Savaglio, et al. 2009

GRB 050904Kawai et al. 2006

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Reionization

12

Star Formation Rate