arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 0901.3194astro-ph.CO
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更新的伽马射线暴哈勃图

An updated Gamma Ray Bursts Hubble diagram

V. F. Cardone, S. Capozziello, M. G. Dainotti

摘要:

伽马射线暴(GRB)作为一种将哈勃图扩展到极高红移的可能途径,近来引起了人们的广泛关注。为此,必须从与距离无关的量的相关性来评估红移z处伽玛暴的亮度(或各向同性发射能量),以便可以求解亮度距离D_L(z),从而求解距离模量μ(z)。Schaefer(2007)对五个不同的两参数相关性进行平均,并使用基准宇宙学模型对其进行校准,编制了69个具有测量mu(z)的伽玛暴样本,该样本从那时起被广泛用于约束宇宙学参数。我们在这里从多个方面更新了该样本。首先,我们添加了最近发现的X射线余辉的相关性,并使用贝叶斯启发的拟合方法来校准不同的GRB相关性,假设基准LCDM模型与最近的WMAP 5数据一致。平均超过六个相关性,我们结束了一个新的伽玛射线暴哈勃图包括83个对象。我们还广泛探讨了不同的基准宇宙学模型的影响,考虑如何估计mu(z)的变化作为函数的$(Ω_M, w_0, w_a)$参数的Chevallier-Polarski- Linder现象学暗能量状态方程。为了避免假设{ \it a priori}宇宙学模型的需要,我们提出了一种新的基于模型无关的局部回归估计μ(z)的校准方法,利用Union SNeIa样本来校准GRB相关。这最终给了我们一个由69个伽玛暴组成的伽玛暴哈勃图,其估计的距离模量mu(z)几乎与基础宇宙学模型无关。

英文摘要:

Gamma ray bursts (GRBs) have recently attracted much attention as a possible way to extend the Hubble diagram to very high redshift. To this aim, the luminosity (or isotropic emitted energy) of a GRB at redshift z must be evaluated from a correlation with a distance independent quantity so that one can then solve for the luminosity distance D_L(z) and hence the distance modulus mu(z). Averaging over five different two parameters correlations and using a fiducial cosmological model to calibrate them, Schaefer (2007) has compiled a sample of 69 GRBs with measured mu(z) which has since then been widely used to constrain cosmological parameters. We update here that sample by many aspects. First, we add a recently found correlation for the X - ray afterglow and use a Bayesian inspired fitting method to calibrate the different GRBs correlations known insofar assuming a fiducial LCDM model in agreement with the recent WMAP5 data. Averaging over six correlations, we end with a new GRBs Hubble diagram comprising 83 objects. We also extensively explore the impact of varying the fiducial cosmological model considering how the estimated mu(z) change as a function of the $(Ω_M, w_0, w_a)$ parameters of the Chevallier - Polarski - Linder phenomenological dark energy equation of state. In order to avoid the need of assuming an {\it a priori} cosmological model, we present a new calibration procedure based on a model independent local regression estimate of mu(z) using the Union SNeIa sample to calibrate the GRBs correlations. This finally gives us a GRBs Hubble diagram made out of 69 GRBs whose estimated distance modulus mu(z) is almost independent on the underlying cosmological model.

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