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和爱因斯坦方程的应用得出的宇宙膨胀率之间的微小差异。如果这种张力得到证实，那么主宰宇宙的神秘暗能量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特殊类型恒星的此类方法，这些恒星的寿命即将结束：后渐近巨型分支恒星和行星状星云。这两个物体都显示出作为精确距离测量工具的巨大前景，但它们的使用受到技术的限制。新的大型仪器和8米级望远镜的出现改变了这一点。该团队将分析来自这类仪器的现有和新数据，以确定其中一种方法或两种方法是否都能解决目前宇宙学中的紧张局势。宇宙起源和演化的问题是天体物理学以外的人非常感兴趣的问题，是让所有教育水平的学生参与进来的极好方式。该项目包括一项重要的公共外联方案，通过一系列地方外联活动，面向K-12级和普通公众。此外，该项目将帮助培训目前在大学里的一代科学家，让他们直接参与这项研究工作。基于目前的测量，根据造父变星对SNIa的校准确定的哈勃常数与由宇宙微波背景功率谱和宇宙学常数假设组合得出的哈勃常数并不是很匹配。为了测试这种哈勃张力是真实的，还是仅仅是由系统误差驱动的伪像，需要额外的高精度河外距离指示器。这个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~10MPC以内的静止星系产生~2%的距离误差，并直接与GAIA测量有关；该技术必须在银河系外校准，但可以应用于所有在~40MPC内V波段绝对亮度大于-20的星系，并且可以将距离小于8%的SNIa的数量增加一个数量级。这两种方法的发展都是由于两台大型整场单位光谱仪的出现：Hobby-Eberly望远镜上的Virus和欧洲甚大望远镜上的MUSE。来自这些仪器的数据将允许团队确定其中一种或两种方法是否能够达到测试哈勃张力是否真实所需的精度，因此需要新的物理学来解释它。这一裁决反映了NSF的法定使命，并通过使用基金会的智力优势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.