Talk detail

Participant	Yonetoku, Daisuke
Institution	Kanazawa University - Kakuma - Kanazawa - Ishikawa - Japan

Session	OC3	Accepted	Yes	Order	2	Time	14:20 - 14:40
Talk	Oral abstract	Title	Star Formation Rate, Reionization, and Early Metal Enrichment Probing with GRBs
Co-authors	Toshio Murakami, Ryo Tsutsui, Takashi Nakamura, Keitaro Takahashi
Abstract	Gamma-ray bursts (GRBs) are the brightest explosions in the universe, and associated with the massive star explosions. Therefore, GRBs can be the most promising tool to probe the star formation activity at the high redshift universe. Some empirical correlations between the spectral peak energy and the brightness of prompt GRBs are reported by Amati et al.(2002), Yonetoku et al.(2004), Ghirlanda et al.(2004), and so on. They can be used as a luminosity (also redshift) indicators. As a demonstration, we investigated the redshift distribution of GRBs using $\sim 700$ GRBs observed with BATSE. For the redshift range of $0 \le z \le 2$, the GRB formation rate increases and is well correlated with the star formation rate, while it keeps constant toward $z \sim 12$. We also discuss the cosmic reionization and the early metal enrichment based on the estimated GRB formation rate. In this talk, including the recent observation results on the GRB cosmology, we introduce the usage of GRBs as the cosmological probing tool.