来自星系透镜的哈勃常数：三轴性和模型简并的影响
The Hubble constant from galaxy lenses: impacts of triaxiality and model degeneracies
摘要：
哈勃常数可以用引力透镜源的多个图像之间的时间延迟来约束。在一些值得注意的情况下，典型的透镜分析假设等温星系密度剖面产生较低的哈勃常数值，与HST关键项目的结果（72 +- 8 km/s/Mpc）不一致。从星系透镜系统中推导出的哈勃常数值的可能系统性可能是由许多因素造成的，例如忽略环境影响、等温假设或视线结构的污染。另一个潜在的重要因素是透镜星系晕的三轴结构;大多数透镜模型仅仅通过扰动投影的球面透镜势来解释晕的形状，这种近似通常是必要的，但在CDM范式中预测的三轴度水平上是不够的。为了量化这种假设在估计哈勃参数中引入的潜在误差，我们强烈地通过三轴软化等温晕的样本对遥远的星系进行透镜，并使用MCMC方法来约束由此产生的多个图像系统的透镜晕轮廓和哈勃参数。我们探索哈勃参数和透镜模型的几个参数之间的主要退化，发现如果没有一种方法来准确地打破这些退化的哈勃参数的准确估计是不可能的。至关重要的是，我们发现，三轴性并没有显着的偏见估计的哈勃常数，并提供了一个分析解释这种行为的情况下，等温配置文件。被忽视的三轴晕形状不能有助于低哈勃常数值在一些星系透镜系统。
英文摘要：
The Hubble constant can be constrained using the time delays between multiple images of gravitationally lensed sources. In some notable cases, typical lensing analyses assuming isothermal galaxy density profiles produce low values for the Hubble constant, inconsistent with the result of the HST Key Project (72 +- 8 km/s/Mpc). Possible systematics in the values of the Hubble constant derived from galaxy lensing systems can result from a number of factors, e.g. neglect of environmental effects, assumption of isothermality, or contamination by line-of-sight structures. One additional potentially important factor is the triaxial structure of the lensing galaxy halo; most lens models account for halo shape simply by perturbing the projected spherical lensing potential, an approximation that is often necessary but that is inadequate at the levels of triaxiality predicted in the CDM paradigm. To quantify the potential error introduced by this assumption in estimates of the Hubble parameter, we strongly lens a distant galaxy through a sample of triaxial softened isothermal halos and use an MCMC method to constrain the lensing halo profile and the Hubble parameter from the resulting multiple image systems. We explore the major degeneracies between the Hubble parameter and several parameters of the lensing model, finding that without a way to accurately break these degeneracies accurate estimates of the Hubble parameter are not possible. Crucially, we find that triaxiality does not significantly bias estimates of the Hubble constant, and offer an analytic explanation for this behaviour in the case of isothermal profiles. Neglected triaxial halo shape cannot contribute to the low Hubble constant values derived in a number of galaxy lens systems.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
