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Statistics of structures in the gravitational potential - a possible way to constrain halo populations without reference to mass

引力势结构的统计——一种在不参考质量的情况下约束晕圈群体的可能方法

基本信息

批准号：
106639007
负责人：
Professor Dr. Matthias Bartelmann
金额：
--
依托单位：
Institut für Theoretische Physik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2009
资助国家：
德国
起止时间：
2008-12-31 至 2011-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/106639007?language=en
关键词：
Statistics structures gravitational potential possible

项目摘要

The distribution of dark-matter halos with mass is one of the central predictions of the standard cosmological model. The Press-Schechter mass function or variants thereof predict the mass function of dark-matter halos. Although based on questionably simple assumptions, numerical simulations confirm it with astonishing accuracy. The mass function of real dark-matter halos is in principle simple and in practice very difficult to measure. The main problem is that mass is not an astronomical observable. Mass is inferred from kinematic or dynamical observables such as the motion of tracers, the temperature of hot gas, or from light deflection by gravitational lensing. None of these observables measures mass, but rather the depth of the gravitational potential or derivatives thereof. Mass is obtained only after integrating local information within some volume which is typically arbitrarily defined, and whose centre is typically uncertain. Proxies to the mass, such as X-ray temperature or luminosity, help practically to some degree, but do not conceptually improve the situation. Besides, they introduce calibration uncertainties. The question thus arises whether distribution functions of observable quantities can directly be predicted without reference to mass. Having completed a successful pilot study, we propose to investigate distribution functions of structures in the gravitational potential, which are directly related to local observables such as temperatures, velocity dispersions or gravitational-lensing effects. The statistics of potential sinks of sufficient depth and size can be derived from the theory of Gaussian random fields, allowing the direct prediction of, e.g., X-ray temperature functions which agree very well with the observations at least at the high-mass end. Within the proposed project, we wish to extend and improve our prototype method such that distribution functions of several observables can directly be predicted on all scales.

暗物质晕随质量的分布是标准宇宙学模型的中心预测之一。Press-Scheck hter质量函数或其变体预测了暗物质晕的质量函数。尽管基于令人怀疑的简单假设，但数值模拟以惊人的准确性证实了这一点。真正的暗物质晕的质量函数原则上很简单，但实际上很难测量。主要的问题是，质量不是天文可观测的。质量是从运动学或动力学观测中推断出来的，例如示踪剂的运动、热气体的温度，或通过引力透镜的光偏转。这些可观测的物质都不是测量质量，而是测量引力势或其导数的深度。只有在将局部信息整合到通常任意定义且其中心通常是不确定的某个体积内之后，才能获得质量。质量的替代物，如X射线温度或光度，在某种程度上实际上是有帮助的，但在概念上并不能改善这种情况。此外，它们还引入了校准不确定度。由此产生的问题是，是否可以直接预测可观测量的分布函数而不参考质量。在完成了一项成功的初步研究后，我们建议研究结构在引力势中的分布函数，这些分布函数与局部观测数据直接相关，如温度、速度色散或引力透镜效应。足够深度和大小的势汇的统计数据可以从高斯随机场理论中得到，从而可以直接预测X射线温度函数，这些函数至少在高质量端与观测结果非常吻合。在建议的项目中，我们希望扩展和改进我们的原型方法，以便可以在所有尺度上直接预测几个观测值的分布函数。