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arXiv 0904.4381astro-ph.CO
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SLACS引力透镜的密度分布、速度各向异性和视线外会聚

Density profile, velocity anisotropy and line-of-sight external convergence of SLACS gravitational lenses

Antonio C. C. Guimarães, Laerte Sodré

摘要:

利用斯隆透镜ACS巡天观测到的58个强透镜事件的数据,通过两种独立的方法:恒星动力学和强引力透镜,估算了它们的爱因斯坦半径内的投影星系质量。我们进行了联合分析,这两个估计模型内的透镜密度分布,恒星速度各向异性和视线(LOS)的外部收敛,其中包括强透镜效应的大尺度结构的影响,具有高达三个自由度。采用贝叶斯分析来估计模型参数,评估其显著性并比较模型。我们发现,数据有利于贾菲的光剖面Hernquist的,但这两者之间的任何特定的选择并不改变定性的结论,我们调查的系统的功能。的密度分布是兼容的等温,是稍微陡峭,并具有不确定性的对数斜率的顺序为5%的模型,考虑到各向异性和外部收敛的先验知识。我们确定了一个相当大的退化之间的密度剖面斜率和各向异性参数,这在很大程度上增加了这些参数的估计的不确定性,但我们没有遇到任何证据,有利于平均为整个样本的各向异性速度分布。由宇宙学给出的先验概率分布后的LOS外部收敛对透镜密度分布的估计有很小的影响,但可以增加其值的色散近40%。

英文摘要:

Data from 58 strong-lensing events surveyed by the Sloan Lens ACS Survey are used to estimate the projected galaxy mass inside their Einstein radii by two independent methods: stellar dynamics and strong gravitational lensing. We perform a joint analysis of these two estimates inside models with up to three degrees of freedom with respect to the lens density profile, stellar velocity anisotropy, and line-of-sight (LOS) external convergence, which incorporates the effect of the large-scale structure on strong lensing. A Bayesian analysis is employed to estimate the model parameters, evaluate their significance and compare models. We find that the data favor Jaffe's light profile over Hernquist's, but that any particular choice between these two does not change the qualitative conclusions with respect to the features of the system that we investigate. The density profile is compatible with an isothermal, being sightly steeper and having an uncertainty in the logarithmic slope of the order of 5% in models that take into account a prior ignorance on anisotropy and external convergence. We identify a considerable degeneracy between the density profile slope and the anisotropy parameter, which largely increases the uncertainties in the estimates of these parameters, but we encounter no evidence in favor of an anisotropic velocity distribution on average for the whole sample. An LOS external convergence following a prior probability distribution given by cosmology has a small effect on the estimation of the lens density profile, but can increase the dispersion of its value by nearly 40%.

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