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arXiv 0805.0875astro-phgr-qchep-ph
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用标准烛光测试伽玛暴

Testing GRBs as Standard Candles

S. Basilakos, L. Perivolaropoulos

摘要:

近年来,在伽玛射线暴观测量与红移之间发现了几种相关性。适当的评估和校准这些相关性可能有助于使用伽玛射线暴作为标准烛光约束宇宙的膨胀历史的红移$z>6$。在这里,我们使用69 GRB数据集最近编译的Schaefer(astro-ph/0612285),我们测试的校准上述相关性($1:\epkk-E_γ$,$2:\epkk-L$,$3:\tlag-L$,$4:V-L$,$5:\trt-L$)的两个潜在的系统学来源:红移和宇宙学模型中使用的校准。在检查模型依赖性时,我们假设平坦的\lcdm和变化的$\omm$。我们的方法避免了以前的研究中的循环问题,因为我们没有固定的$\omm$找到相关参数。相反,我们同时最小化$χ^2$的对数线性相关参数$a$,$b$和宇宙学参数$\omm$。我们发现没有统计学上显着的证据红移依赖$a$和$b$在任何相关关系测试。我们还发现,测试的五个相关关系($\epkk-E_γ$)之一,有一个显着较低的固有色散相比,其他相关性。对于这种关联关系,最大似然法倾向于宇宙常数的存在,而其他四种关联则倾向于扁平物质主导的宇宙$\omm \simeq 1$。最后,对不同$\omm$值的GRB和SnIa数据进行了互相关分析,结果表明,$E_{peak}-E_γ$关系很好地跟踪了SnIa红移区域。然而,即使是最紧密的相关关系($E_{peak}-E_γ$)对$\omm$的约束也比当前的SnIa数据弱得多。

英文摘要:

Several correlations among Gamma Ray Burst (GRB) observables with available redshifts have been recently identified. Proper evaluation and calibration of these correlations may facilitate the use of GRBs as standard candles constraining the expansion history of the universe up to redshifts of $z>6$. Here we use the 69 GRB dataset recently compiled by Schaefer (astro-ph/0612285) and we test the calibration of five of the above correlations ($1:\epkk-E_γ$, $2:\epkk-L$, $3:\tlag-L$, $4:V-L$, $5:\trt-L$) with respect to two potential sources of systematics: Evolution with redshift and cosmological model used in the calibration. In examining the model dependence we assume flat \lcdm and vary $\omm$. Our approach avoids the circularity problem of previous studies since we do not fix $\omm$ to find the correlation parameters. Instead we simultaneously minimize $χ^2$ with respect to both the log-linear correlation parameters $a$, $b$ and the cosmological parameter $\omm$. We find no statistically significant evidence for redshift dependence of $a$ and $b$ in any of the correlation relations tested. We also find that one of the five correlation relations tested ($\epkk-E_γ$) has a significantly lower intrinsic dispersion compared to the other correlations. For this correlation relation, the maximum likelihood method favors the existence of a cosmological constant while the other four correlation favor a flat matter dominated universe $\omm \simeq 1$. Finally, a cross-correlation analysis between the GRBs and SnIa data for various values of $\omm$ has shown that the $E_{peak}-E_γ$ relation traces well the SnIa redshift regime. However, even the tightest correlation relation ($E_{peak}-E_γ$) provides much weaker constraints on $\omm$ than current SnIa data.

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