arXiv 1306.44152013-06astro-ph.HEastro-ph.CO

利用伽玛暴的宇宙学检验、恒星形成率和可能的绝对演化

Cosmological Tests Using GRBs, the Star Formation Rate and Possible Abundance Evolution

Jun-Jie Wei, Xue-Feng Wu, Fulvio Melia, Da-Ming Wei, Long-Long Feng

备注：: 25 pages, 5 figures, 2 tables, accepted for publication in MNRAS. arXiv admin note: text overlap with arXiv:1109.0990 by other authors
DOI：: 10.1093/mnras/stu166

摘要：

本文的主要目标是利用调和斯威夫特长伽玛射线暴（LGRB）与恒星形成历史（SFH）的尝试，比较$Λ$ CDM的预测与$R_{\rm h}=ct$宇宙中的预测。在前者的背景下，我们确认，最新的雨燕样本的伽玛暴揭示了一个不断增加的演变，在伽玛暴率相对于恒星形成率（SFR）在高红移。观测到的伽玛射线暴速率和SFR之间的差异可以通过假设一个参数为$(1+z)^{0.8}$的适度演化来消除-也许表明金属丰度的宇宙演化。然而，我们发现$Z=0.52Z_{\odot}$的金属丰度切割比以前的研究中看到的更高，这表明LGRB优先发生在金属贫乏的环境中，即，$Z\sim0.1-0.3Z_{\odot}$。我们对高\emph{z}（$\ga 3.8$）SFH使用简单的幂律近似，即，$R_{\rm SF}\propto[(1+z)/4.8]^α$，以检查高-\emph{z} SFR如何可能受到雨燕伽玛暴样品中可能的丰度演变的影响。对于与$Λ$ CDM一致的膨胀历史，我们发现，如果$α=-2.41_{-2.09}^{+1.87}$，Swift红移和光度分布可以以合理的精度再现。对于$R_{\rm h}=ct$宇宙，GRB率与$Λ$ CDM略有不同，但也需要额外的进化效应，金属丰度切割为$Z=0.44Z_{\odot}$。假设SFR和GRB率通过演化的金属丰度相关，我们发现GRB数据限制$R_{\rm h}=ct$中高\emph{z} SFR的斜率为$α=-3.60_{-2.45}^{+2.45}$。这两种宇宙学都与GRB/SFR数据相当吻合。

英文摘要：

The principal goal of this paper is to use attempts at reconciling the Swift long gamma-ray bursts (LGRBs) with the star formation history (SFH) to compare the predictions of $Λ$CDM with those in the $R_{\rm h}=ct$ Universe. In the context of the former, we confirm that the latest Swift sample of GRBs reveals an increasing evolution in the GRB rate relative to the star formation rate (SFR) at high redshifts. The observed discrepancy between the GRB rate and the SFR may be eliminated by assuming a modest evolution parameterized as $(1+z)^{0.8}$---perhaps indicating a cosmic evolution in metallicity. However, we find a higher metallicity cut of $Z=0.52Z_{\odot}$ than was seen in previous studies, which suggested that LGRBs occur preferentially in metal poor environments, i.e., $Z\sim0.1-0.3Z_{\odot}$. We use a simple power-law approximation to the high-\emph{z} ($\ga 3.8$) SFH, i.e., $R_{\rm SF}\propto[(1+z)/4.8]^α$, to examine how the high-\emph{z} SFR may be impacted by a possible abundance evolution in the Swift GRB sample. For an expansion history consistent with $Λ$CDM, we find that the Swift redshift and luminosity distributions can be reproduced with reasonable accuracy if $α=-2.41_{-2.09}^{+1.87}$. For the $R_{\rm h}=ct$ Universe, the GRB rate is slightly different from that in $Λ$CDM, but also requires an extra evolutionary effect, with a metallicity cut of $Z=0.44Z_{\odot}$. Assuming that the SFR and GRB rate are related via an evolving metallicity, we find that the GRB data constrain the slope of the high-\emph{z} SFR in $R_{\rm h}=ct$ to be $α=-3.60_{-2.45}^{+2.45}$. Both cosmologies fit the GRB/SFR data rather well.

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摘要：

英文摘要：

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