# Presentation: 806419

## Pop-III Star Formation Rate Inferred from

** ****Ep – Luminosity Relation of Gamma-Ray Bursts **

**Daisuke Yonetoku **(Kanazawa Univ.)

- Introduction (GRB property, Star Formation Rate)
- Spectral Analyses and Ep – luminosity Relation
- Redshift Distribution and GRB Formation Rate
- “Reionization” and “Metal Pollution”

** ****yonetoku@astro.s.kanazawa-u.ac.jp**

## Star Formation Rate

- z = 10

-  z = 0

- z = 30

- z = 1089

- Star Formation Rate measured
- by UV, optical and IR rapidly
- increase toward z = 1, and
- keep flat at higher redshift.

- Giavalisco et al. 2003

**Star Formation Rate**

- CMB

- Dark Age

- Big
- Bang

- First Star

- First SNe
- Black Hole

- Primordial
- Galaxy

- Present Age

## Ep – Luminosity (Yonetoku) Relation

- 970508   970828   971214
- 980326   980329   980703
- 990123   990506   990510
- 991216   000131

- 970228   980613   990705
- 990712   000214   010222
- 011121   011211   020405

- 050603   050525   050401040924   050904

**Swift–Konus**

**CGRO–BATSE**

**Beppo–SAX**

**HETE–2**

- 010921   020124   020813
- 021004   021211   030226030328   030329   030429

**Integral**

- 041218

- 35

- Lp ∝ [Ep(1+z)]2.0

**050904**
**z=6.3**

## Redshift Distribution

**Redshift Distribution**

**Flux Limit (2e-7 erg/cm****2****/s)**

- effective observation time
- of BATSE = 4.5 years
- number of GRB = 700 events

- Redshift estimation from Ep – L

- Salpeter IMF
- > 40 Msun

- Top
- Heavy
- 100-140 Msun

## Star Formation Rate

- Star Formation Rate (Giavalisco et al. 2004)

- ・ Star Formation Rate from GRB (Murakami et al. 2005)
- ・ Jet Angle Evolution θj ∝ (1+z)-0.45 (Yonetoku et al. 2005)

**Star Formation Rate**

## The Latest Star Formation Rate  

- Both Star Formation Rates show declinetoward the higher redshift.
- (2006/Sep/14 , Nature)

- ※absorption correction is    not adopted.

## Pop-III Spectrum

- Lyα- line

- Brems. from nebula
- (T=3×104 K)

- BB radiation from Pop-III
- (T=105 K, L = LEDD)

- 13.6eV

- (1216Å)

- escape fraction : fesc = 0

- B.B.

- Lyα

**Pop-III Spectrum**

- nebula

## Star Formation and Early Epoch Reionization

**Star Formation and Early Epoch Reionization**

- z = 1089 : Recombination (CMB)

- All elements are ionized at the Big Bang
-        Synthesized materials are Hydrogen and Helium

- Birth of the first stars (composed by H and He)

- 11 < z < 19 : Reionization

- IGM Metallicity measured by QSO

- Songaila 2001

- When and What generates the heavy elements with abundance of 10-4Zsun in the IGM?

- Is the Star Formation Rate large enough to reionize the universe?

## Cosmic Reionization

- Stars with above 50Msun have the temperature of 105 K and
- brighten with the Eddington Luminosity for 106 yrs

**Cosmic Reionization**

- Initial Mass Function of
- the population-III stars

- (m > 50 Msun)

- (m < 50 Msun)

- ρGRB = 104 events/Gpc3/yr

- UV photon with hν>13.6eV = 8.75×1068 (photon/Gpc3/yr)

- Baryon number density =

- =  7.66×1075 (Gpc-3)

- Nakamura & Umemura 2001

- (α=β=2.35)

## Metal Pollution in IGM

- (Msun/Gpc-3/yr)

- Star Formation Rate

- Metal abundance reaches Z = 1.2×10-4 Zsun,
- if the Pop-III star formation keeps for 107 yrs.

- Metal production from stellar explosion

## Conclusions

- ● Ep – Luminosity relation can be confirmed in 35 known     redshift samples. Further analysis is in progress.

- ● Using the Ep – Luminosity relation as a redshift indicator,
-     we estimated the Star Formation Rate.

- ● We show the possibility that
-      『Cosmic reionization』 and 『Metal pollution in the IGM』 may
-      be realized within the short time interval of 107-8 yrs.