Can Gamma-Ray Bursts Be Used to Measure Cosmology? A Further Analysis
Can Gamma-Ray Bursts Be Used to Measure Cosmology? A Further Analysis
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DOI：
10.1086/466509
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发表时间：
2005-01
期刊：
影响因子：
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通讯作者：
Duo Xu;Z. Dai;E. Liang;E. Liang;E. Liang
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文献类型：
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作者：
Duo Xu;Z. Dai;E. Liang;E. Liang;E. Liang
自从Ghirlanda等人提出γ射线暴喷注的γ射线能量Eγ与暴标架中νFν谱的峰值能量Ep之间的关系以来，人们提出了三种不同的γ射线暴宇宙学测量方法。在方法I中，为了计算一个有利宇宙学的概率，只考虑已经最适合这个宇宙学的Eγ-Ep关系的贡献。我们将这种方法应用于17个伽玛暴的样本，得到了一个平坦的ΛCDM宇宙的质量密度ΩM = 0.15（1 σ）。在方法II中，为了计算某些宇宙学的概率，考虑了所有可能的Eγ-Ep关系的贡献，这些关系最适合于它们相应的宇宙学。用这种方法，我们找到了一个平坦宇宙的质量密度为0.14 < ΩM < 0.69（1 σ）的约束。在方法III中，为了得到某些宇宙学的概率，考虑了所有可能的Eγ-Ep关系与它们的不等权重相关的贡献。利用这种方法，我们得到了一个令人鼓舞的约束：对于平坦宇宙，质量密度为0.16 < ΩM < 0.45（1 σ）;对于ΩM = 0.27的和谐模型，质量密度为χ = 19.08/15 = 1.27。与前两种方法相比，方法III使观测到的17个伽玛暴在相同的置信水平下具有更严格的置信区间。此外，我们进行了蒙特卡罗模拟，并使用更大的样本调查伽玛暴的宇宙学能力与不同的方法。我们发现，无论Eγ-Ep关系是否被低z暴校准，更大的GRB样本都可以用来有效地测量宇宙学。在雨燕时代持续观测伽玛暴有望使伽玛暴的宇宙学效用从婴儿期进展到童年期。
Three different methods of measuring cosmology with gamma-ray bursts (GRBs) have been proposed since a relation between the gamma-ray energy Eγ of a GRB jet and the peak energy Ep of the νFν spectrum in the burst frame was reported by Ghirlanda and coauthors. In method I, to calculate the probability for a favored cosmology, only the contribution of the Eγ-Ep relation that is already best-fitted for this cosmology is considered. We apply this method to a sample of 17 GRBs and obtain the mass density ΩM = 0.15 (1 σ) for a flat ΛCDM universe. In method II, to calculate the probability for some certain cosmology, contributions of all the possible Eγ-Ep relations that are best-fitted for their corresponding cosmologies are taken into account. With this method, we find a constraint on the mass density 0.14 < ΩM < 0.69 (1 σ) for a flat universe. In method III, to obtain the probability for some cosmology, contributions of all the possible Eγ-Ep relations associated with their unequal weights are considered. With this method, we obtain an inspiring constraint on the mass density 0.16 < ΩM < 0.45 (1 σ) for a flat universe and χ = 19.08/15 = 1.27 for the concordance model of ΩM = 0.27. Compared with the previous two methods, method III makes the observed 17 GRBs place much more stringent confidence intervals at the same confidence levels. Furthermore, we perform a Monte Carlo simulation and use a larger sample to investigate the cosmographic capabilities of GRBs with different methods. We find that a larger GRB sample could be used to effectively measure cosmology, no matter whether the Eγ-Ep relation is calibrated by low-z bursts or not. Ongoing observations of GRBs in the Swift era are expected to make the cosmological utility of GRBs progress from its babyhood into childhood.