Integral Field Spectroscopy and the Hubble Constant

可以说，当今宇宙学中最重要的问题是哈勃张力，即局部测量的宇宙膨胀率与从早期宇宙的基本物理学和爱因斯坦方程的应用中推断出来的宇宙膨胀率之间的微小差异。如果这种张力得到证实，那么支配宇宙的神秘暗能量甚至比爱因斯坦想象的还要复杂，需要新的物理学来解释宇宙的膨胀历史。为了解决这个问题，我们需要使用尽可能多的独立方法来测量到星系的精确距离。宾夕法尼亚州立大学的科学家们提议开发和测试两种基于生命接近尾声的特殊类型恒星的方法：后渐近巨型分支恒星和行星状星云。作为测量精确距离的工具，这两个物体都显示出巨大的前景，但它们的使用受到技术的限制。新型大型仪器与8米级望远镜的结合改变了这一点。该团队将分析来自这些仪器的现有数据和新数据，以确定其中一种或两种方法是否可以解决当前宇宙学中的紧张局势。宇宙的起源和演化问题是天体物理学领域以外的人非常感兴趣的问题，也是吸引各级教育学生的好方法。该项目包括一项重要的公共宣传计划，通过一系列当地的宣传活动，针对K-12年级和普通公众。此外，该项目将帮助培养现在在大学里的新一代科学家，让他们直接参与这项研究工作。根据目前的测量，从造父变星对SNIa的校准中确定的哈勃常数与宇宙微波背景功率谱和宇宙常数假设相结合得出的哈勃常数并不完全匹配。为了测试哈勃望远镜的张力是真实存在的，还是系统误差造成的假象，我们需要额外的高精度星系外距离指示器。这项提议的目标是开发和测试两个这样的标准蜡烛：后渐近巨型分支恒星和行星状星云光度函数。前者有可能对~10 Mpc内的静止星系产生~2%的距离误差，并与盖亚测量直接相关；该技术必须在银河系外进行校准，但可以应用于~40 Mpc内绝对v波段亮度大于-20的所有星系，并且可以将距离低于8%的SNIa数量增加一个数量级。这两种方法的发展都是由于两个大型积分场单位光谱仪的可用性：霍比-埃伯利望远镜上的病毒和欧洲甚大望远镜上的MUSE。来自这些仪器的数据将使研究小组确定其中一种或两种方法是否都能达到测试哈勃张力是否真实所需的精度，从而需要新的物理学来解释它。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Arguably, the most important question in cosmology today is that of the Hubble tension, i.e., the small discrepancy between the expansion rate of the universe measured locally, and that inferred from the basic physics of the early universe and the application of Einstein’s equations. If this tension is confirmed, then the mysterious Dark Energy that dominates the universe is more complex than even Einstein imagined, and new physics is needed to explain the expansion history of the universe. To address this problem, we need to measure precise distances to galaxies using as many independent methods as possible. Scientists at the Pennsylvania State University propose to develop and test two such methods based on special types of stars that are near the end of their lifetimes: post-asymptotic giant branch stars, and planetary nebulae. Both objects have shown tremendous promise as tools for measuring precise distances, but their use has been limited by technology. The availability of new, large-scale instruments combined with 8-meter class telescopes has changed this. The team will analyze both existing and new data from such instruments to determine whether either or both methods can address the current tension in cosmology. Questions of the origin and evolution of the universe are of great interest to people outside the world of astrophysics and are an excellent way to engage students at all levels of education. This project includes a significant program of public outreach targeted at both the K-12 level and the general public through a series of local outreach events. In addition, the project will help train the generation of scientists now in college by involving them directly in this research effort.Based on current measurements, the Hubble Constant determined from the Cepheid calibration of SNIa does not quite match that derived from the combination of the power spectrum of the cosmic microwave background and the assumption of a Cosmological Constant. To test whether this Hubble tension is real or just an artifact driven by systematic errors, there is a need for additional high-precision extragalactic distance indicators. The goal of this proposal is to develop and test two such standard candles: post-asymptotic giant branch stars and the planetary nebula luminosity function. The former has the potential to produce ~2% distance errors to quiescent galaxies within ~10 Mpc and is tied directly to Gaia measurements; the technique must be calibrated outside the Galaxy, but can be applied to all galaxies with absolute V-band magnitudes brighter than -20 within ~40 Mpc, and can increase the number of SNIa with sub-8% distances by an order of magnitude. The development of both methods is made possible by the availability of two large-scale integral-field unit spectrographs: VIRUS on the Hobby-Eberly Telescope and MUSE on the European Very Large Telescope. The data from these instruments will allow the team to determine whether either or both methods can reach the precision needed to test whether the Hubble tension is real and thus requires new physics to explain it.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.