主要内容:
说现在观测到的暴15%的红移大于4，还有大于14的被观测了。
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| Title: |
| Simulations on high-z long gamma-ray burst rate |
| Authors: |
| Qin, Shu-Fu; Liang, En-Wei; Lu, Rui-Jing; Wei, Jian-Yan; Zhang, Shuang-Nan |
| Affiliation: |
| AA(Department of Physics, Guangxi University, Nanning 530004, China), AB(Department of Physics, Guangxi University, Nanning 530004, China), AC(Department of Physics, Guangxi University, Nanning 530004, China), AD(National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing, China), AE(Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China; Physics Department, University of Alabama in Huntsville, Huntsville, AL 35899, USA) |
| Publication: |
| Monthly Notices of the Royal Astronomical Society, Volume 406, Issue 1, pp. 558-565. (MNRAS Homepage) |
| Publication Date: |
| 07/2010 |
| Origin: |
| WILEY |
| MNRAS Keywords: |
| instrumentation: detectors, stars: evolution, stars: formation, gamma-ray burst: general, stars: luminosity function, mass function, galaxies: high-redshift |
| Abstract Copyright: |
| (c) Journal compilation © 2010 RAS |
| DOI: |
| 10.1111/j.1365-2966.2010.16691.x |
| Bibliographic Code: |
| 2010MNRAS.406..558Q |
Abstract
Since the launch of Swift satellite, the detections of high-z (z > 4) long gamma-ray bursts (LGRBs) have been rapidly growing, even approaching the very early Universe (the record holder currently is z = 8.3). The observed high-z LGRB rate shows significant excess over that estimated from the star formation history. We investigate what may be responsible for this high productivity of GRBs at high-z through Monte Carlo simulations, with effective Swift/Burst Alert Telescope (BAT) trigger and redshift detection probabilities based on current Swift/BAT sample and Compton Gamma-ray Observatory/Burst and Transient Source Experiment LGRB sample. We compare our simulations to the Swift observations via log N - log P, peak luminosity (L) and redshift distributions. In the case that LGRB rate is purely proportional to the star formation rate, our simulations poorly reproduce the LGRB rate at z > 4, although the simulated log N - log P distribution is in good agreement with the observed one. Assuming that the excess of high-z GRB rate is due to the cosmic metallicity evolution or unknown LGRB rate increase parametrized as (1 + z)δ, we find that although the two scenarios alone can improve the consistency between our simulations and observations, incorporation of them gives much better consistency. We get 0.2 < ɛ < 0.6 and δ < 0.6, where ɛ is the metallicity threshold for the production of LGRBs. The best consistency is obtained with a parameter set (ɛ, δ) = (~ 0.4, ~ 0.4), and BAT might trigger a few LGRBs at z ~= 14. With increasing detections of GRBs at z > 4 (~15 per cent of GRBs in current Swift LGRB sample based on our simulations), a window for very early Universe is opening by Swift and up-coming space-based multiband astronomical variable object monitor missions.
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