The early universe up to Z 〜 6 was observed through many methods including the 3 K microwave background. How to study a SFR at the early universe beyond this ? T. Murakami Faculty of Science, Kanazawa University Kakuma Kanazawa Ishikawa Exploring the early universe using GRBs This is my plan to study and not a firm conclusion, still preliminary

The early universe at Z 〜 1000 was really observed with 3 K and give us fruitful informations. However this is only in the radiation field! ｚ〜１０ は ALMA で確実に出来る。 King`s road to explore the objects at z 〜 10 will be in infrared satellites : SIRTIF and the ALMA at sub-millimeter wave band. ALMA will be at 〜 The most recent NASA WMAP satellite ２度

Type-Ia SNEs were used as the standard candle. Micro-lensing SDSS is trying to detect remote objects The most distant QSO is known at z=6.6 but the number counting of the QSOs was up to 3 SDSS How observed up to ｚ〜 6 part-1 ？ SNe Ferguson et al. Ann. Rev. A&A 2001

How SFR was studied up to ｚ〜 4 part-2 ？ The background flux level in optical and UV bands were studied and used to estimate the above SFR at the early universe up to z 〜 5 based on the Hubble data. However it is very hard to explore beyond this to z 〜 10 in this method due to scattering or absorption. In optical and UV SFR Ferguson et al. Ann. Rev. A&A 2001 HDF V~30mag

Present methods cannot tell us and estimate a SFR beyond z 〜 6. ALMA can do but in 〜 2010

Gamma-ray bursts are the brightest explosions in the universe. We can observe the explosions up to z 〜 10 and more. In fact, the most distant one ever recorded was its distance is z=4.5 Z=1.6 Z=3.4

Roughly ~10 GRBs are known their red-shift. The most distant one was ~4.5 These GRBs were rather bright. There are more than 3000 GRBs without known distances in the BATSE catalog. If we can give distances to the dim member, we may estimate a SFR at z~10 with.

Using the 10 GRBs with the known distances, we can give distances to the rest of un-known GRBs. There is a correlation between HR and the reported Z 相関係数 : Cp=0.94 P(N,Cp) = この相関は信頼度は高くないが関係を直線 とする Using the 10 GRBs with the known distances, we can give distances to the rest of un-known GRBs. There is a correlation between HR and the reported Z 相関係数 : Cp=0.94 P(N,Cp) = この相関は信頼度は高くないが関係を直線 とする HR=0.254(z+1) How to give distances to dim GRBs ? These are hardness ratios and Ep L.Amati et al., Astroph/ Wei, D.M Murakami, Yonetoku, Izawa 2002 Ep

Norris et al. ApJ 534, 248, 2000 Fenimore et al., Astroph/ lag Lag and variability are other methods to estimate

Spectral lag-luminosity relation Ioka, Nakamura, 2001, ApJL 554, L163 We know now, GRBs are beaming. thus to estimate more precise distances, we require the beaming angles and also viewing directions Murakami, Yonetoku, Izawa 2003 lag 1+z/ （ 1-cosθ ） OT decay light curve We can estimate beaming angle, but

Using the HR-distance formula found between HRs and the distances, we gave distance to 344 dim GRBs and plot their distributions. data: 344 z<0 are within statistical fluctuation ．

logN(L)-logL We have divided the GRBs into 5 groups in distance and estimated a volume density of the GRB explosion in unit of comoving volume and time Then produce logN-logL plots for each group and then adjust them to align a smooth line There are differences between each curve How estimate a rate of GRBs

Based on the HR-distance relation, lags and variability- luminosity relation, we can estimate GRB rates up to z 〜 10. However we don ’ t know the fraction of GRB rate within the SFR. C~0.94 P(N,C)~0.15% Murakami et al., 2002 in preparation There is a small discrepancy between the SFR derived from the UV and GRBs Madau plot 1996 Ferguson et al Fenimore et al., Astroph/

We estimated a SFR with GRBs in two independent methods. There is no clear saturation in SFR in GRBs but there is a tendency of saturation or decrease in optical data.

calorimeter XRS: 0.1~10 keV HXD: keV XIS keV Fully dedicated for quick GRB localizations will be launched in late We are waiting for quick and accurate locations We require more distant GRBs to conclude. Future missions and future activity Swift ASTRO-E II Astro-E II is the wide band and high quality Spectroscopy mission and will be in 2005 Integral Launched in October

To determine the distances, based on the future GRB satellite, infrared observation will be a key inportant. The Lyman alpha shift to 1 micron in case of z=10. So many are planning to observed GRBs in infrared cooperating SWIFT 1.3mφ Cooled NICMOS Lyman break

GRBs can study a SFR up to ｚ〜 10, but still need a calibration at z =5-7. X-ray flashes or X-ray rich GRBs are Mysterious. Short duration GRBs (1/3) are also another Monster hidden from us. These GRBs might open new understanding of an early universe