Probing the Universe's expansion and gravitational wave sources with ground-based optical telescopes

卡内基梅隆大学的一个研究小组将主要使用暗能量相机（DECam）进行天文瞬变事件的观测活动，重点关注引力波（GW）源，这些引力波源将在即将到来的LIGO/Virgo/KAGRA GW探测器观测运行中探测到（预计在2023-2024年期间）。到目前为止，只有一个电磁（EM）对应的GW双中子星合并已被自信地确定。该项目的目标是发现双中子星并合的新电磁对应物，同时寻找与GW中子星-黑洞并合和大质量恒星双黑洞相关的第一个光学瞬变事件。该团队将利用最先进的差分成像软件管道，以及机器学习方法来识别瞬态并模拟它们的光曲线。最后，该项目将利用DECam观测数据，结合其他地面设施的光谱数据和GW数据，研究GW源的环境，以了解引力波源的起源，并通过一种称为标准警笛法的程序产生哈勃常数H0的新测量值，这是宇宙膨胀率的测量值。作为该计划的一部分，该团队将通过教师培训计划在当地公立高中提供基于DECam新数据的教程，并通过公开讲座和文章向更广泛的社区提供宣传。DECam是目前为数不多的能够在即将到来的GW观测中实现EM对等发现的仪器之一。因此，这个项目在多信使天文学社区中扮演着重要的角色。EM对应的发现使广泛的科学分析成为可能，否则单凭GW数据是不确定的或不可能的。这些问题包括：(1)中子星状态方程的约束；(2)广义相对论的修正；(3)宇宙中最重元素的产生。这个项目的重点是解决天体物理学中两个紧迫的问题：令人费解的“哈勃恒定张力”，不同探测器测量的H0值之间的差异，以及合并双星系统的起源，是否由动态相互作用或恒星演化促进。这个奖项推进了“宇宙大创意之窗”的目标。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。

A research team at Carnegie-Mellon University will carry out an observational campaign of astronomical transient events using primarily the Dark Energy Camera (DECam), with a focus on the gravitational wave (GW) sources that will be detected in the upcoming LIGO/Virgo/KAGRA GW detectors observing run (expected during 2023-2024). So far, only one electromagnetic (EM) counterpart to a GW binary neutron star merger has been confidently identified. The goal of the project is to discover new electromagnetic counterparts to mergers of binary neutron stars, while also searching for the first optical transient events associated with GW neutron star-black hole mergers and massive stellar binary black holes. The team will make use of a state-of-the-art difference imaging software pipeline, and machine learning methods to identify transients and model their light curves. Finally, this program will use the DECam observations, in combination with spectroscopic data from other ground-based facilities and GW data, to study the environment of GW sources to understand the origin of gravitational wave sources, and to produce new measurements of the Hubble constant H0, a measure of the expansion rate of the universe, through a procedure called the standard siren method. As part of this program, the team will provide tutorials based on the new DECam data at local public high schools through the Teachers Training program, and providing outreach to the broader community through public lectures and articles.DECam is one of the very few currently functioning instruments with the capabilities to enable EM counterpart discoveries in the upcoming GW observing run. This project, therefore, serves an important role within the multi-messenger astronomy community. EM counterpart discoveries enable a wide range of scientific analyses that are otherwise inconclusive or impossible with GW data alone. These include constraining (1) the equation of state of neutron stars, (2) modifications to General Relativity, and (3) the production of the heaviest elements in the Universe. This project focuses on addressing two pressing questions in astrophysics: the puzzling “Hubble constant tension”, a discrepancy between values of H0 measured through different probes, and the origin of merging binary systems, whether facilitated by dynamical interactions or by stellar evolution. This award advances the goals of the Windows on the Universe Big Idea.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.