Cosmological parameters from strong gravitational lensing and stellar dynamics in elliptical galaxies
Cosmological parameters from strong gravitational lensing and stellar dynamics in elliptical galaxies
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DOI：
10.1051/0004-6361:20077534
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发表时间：
2007-11
影响因子：
6.5
通讯作者：
C. Grillo;C. Grillo;M. Lombardi;M. Lombardi;G. Bertin
中科院分区：
文献类型：
--
作者：
C. Grillo;C. Grillo;M. Lombardi;M. Lombardi;G. Bertin
上下文对宇宙微波背景辐射、轻元素丰度、星系的大尺度分布和遥远的超新星的观测是确定定义宇宙全球结构的宇宙学参数的主要工具。目标。在这里，我们说明了如何在椭圆星系的强引力透镜和恒星动力学的观测相结合，提供了一个简单的和有前途的方法来测量宇宙物质和暗能量密度参数。方法.一旦知道了系统的临界密度，就可以通过测量爱因斯坦角来获得爱因斯坦圆内封闭的质量的引力透镜估计。一个依赖于模型的动力学估计，这个质量也可以通过测量恒星组件的中心速度色散。假设测试良好的同源1/r 2（等温）的总（亮+暗）密度分布的椭圆星系作为透镜的配置文件，这两个质量测量可以适当地进行比较。由此导出了爱因斯坦角与中心恒星速度色散之间的关系，并由此估算了宇宙物质和暗能量密度参数。结果我们通过模拟确定了宇宙学参数估计的准确性，其中包括相关量的实际测量不确定性。有趣的是，宇宙学参数平面上的预期约束与来自其他观测技术的约束是互补的。然后，我们将该方法应用于斯隆透镜ACS（SLACS）和透镜结构和动力学（LSD）调查的最新数据集，并表明暗能量密度参数在0.7和0.8之间的一致性值包括在我们的99%置信区间内。结论.目前可用的透镜数量很少，这使我们无法精确地确定宇宙学参数，但它仍然证明了该方法的可行性。当应用于由数百个透镜制成的样本时，预计将在即将进行的深度和广度调查中获得，这种技术将成为测量宇宙几何形状的重要替代工具。
Context. Observations of the cosmic microwave background, light element abundances, large-scale distribution of galaxies, and distant supernovae are the primary tools for determining the cosmological parameters that define the global structure of the Universe. Aims. Here we illustrate how the combination of observations related to strong gravitational lensing and stellar dynamics in elliptical galaxies offers a simple and promising way to measure the cosmological matter and dark-energy density parameters. Methods. A gravitational lensing estimate of the mass enclosed inside the Einstein circle can be obtained by measuring the Einstein angle, once the critical density of the system is known. A model-dependent dynamical estimate of this mass can also be obtained by measuring the central velocity dispersion of the stellar component. By assuming the well-tested homologous 1/r 2 (isothermal) profile for the total (luminous+dark) density distribution in elliptical galaxies acting as lenses, these two mass measurements can be properly compared. Thus, a relation between the Einstein angle and the central stellar velocity dispersion is derived, and the cosmological matter and the dark-energy density parameters can be estimated from this. Results. We determined the accuracy of the cosmological parameter estimates by means of simulations that include realistic measurement uncertainties on the relevant quantities. Interestingly, the expected constraints on the cosmological parameter plane are complementary to those coming from other observational techniques. Then, we applied the method to the recent data sets of the Sloan Lens ACS (SLACS) and the Lenses Structure and Dynamics (LSD) Surveys, and showed that the concordance value between 0.7 and 0.8 for the dark-energy density parameter is included in our 99% confidence regions. Conclusions. The small number of lenses available to date prevents us from precisely determining the cosmological parameters, but it still proves the feasibility of the method. When applied to samples made of hundreds of lenses that are expected to become available from forthcoming deep and wide surveys, this technique will be an important alternative tool for measuring the geometry of the Universe.