A New Probe of the Magnetic Interstellar Medium

天文研究表明，我们的宇宙始于大约137亿年前的大爆炸。用现代望远镜，我们可以追溯宇宙在大爆炸后的几分钟内的历史。但我们能解释大爆炸本身吗？它是由什么引起的？“通胀理论”试图做到这一点。如果膨胀理论是正确的，那么宇宙中的所有结构，从星系团到恒星和行星，都是从大爆炸期间产生的时空微小波动开始的。该理论还在相对论和量子力学之间提供了有趣的联系，相对论解释了宇宙的大尺度属性，量子力学解释了原子的小尺度属性。因此，对通货膨胀理论的检验对科学具有根本性的重要性。根据膨胀理论，在偏振辐射中应该有一个微小的信号，在每个方向都可以看到。研究人员是在宇宙微波背景(CMB)中寻找这一微弱信号的大型国际努力的一部分。为了测试这个模型，研究小组必须准确地测量我们银河系中尘埃云的偏振，因为银河系会产生类似的微弱偏振光。这个团队设计并制造了两个革命性的仪器来测量来自数百万颗恒星的光的偏振。这些测量将使团队能够区分银河系中尘埃造成的偏振与大爆炸遗留下来的偏振。这位研究人员将为加州理工大学现有的教育和推广活动做出贡献，包括努力与纳瓦霍地区的学生合作，向他们介绍射电天文学。研究人员基于Wollaston棱镜的一种新应用，开发了广域线性光学偏振仪(WALOP)。一次曝光即可测量恒星的线偏振。这一点非常重要，因为人们需要以高于0.1%的精度测量偏振，而连续曝光之间大气的微小变化可能会导致这一水平的系统误差。该小组将在克里特岛部署一个WALOP，在南非部署另一个。他们将调查银河系中受尘埃污染最少的两个天球部分，即银河系北极帽和南极帽周围。这将使恒星偏振测量的数量从大约35,000个增加到超过400,000个。他们将使用恒星偏振测量和恒星距离测量来追踪银河系磁场。研究人员将在了解银河系磁场结构和确定银河系尘埃对CMB极化信号的影响方面做出重大贡献。这一奖项反映了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。

Astronomical research reveals that our universe began with a Big Bang, about 13.7 billion years ago. With modern telescopes we can trace the history of the universe from a few minutes after the Big Bang. But can we explain the Big Bang itself and what gave rise to it? The “Inflationary Theory” attempts to do just that. If Inflationary Theory is correct, then all the structure in the universe, from clusters of galaxies to stars and planets, started as tiny fluctuations in spacetime that were created during the Big Bang. The theory also provides a fascinating link between relativity, which explains the large-scale properties of the universe, and quantum mechanics, which explains the small-scale properties of atoms. Tests of the Inflationary Theory are therefore of fundamental importance to science. According to the Inflationary Theory, there should be a tiny signal in polarized radiation, visible in every direction. The investigators are part of a large international effort to find this faint signal in the Cosmic Microwave Background (CMB). To test the model, the team must accurately measure the polarization from dust clouds in our Milky Way galaxy, which produces a similar kind of faint polarized light. This team has designed and built two revolutionary instruments to measure the polarization of the light from millions of stars. These measurements would enable the team to discriminate polarization due to dust in the Milky Way from that left over from the Big Bang. The investigator will contribute existing education and outreach activities at Cal Tech, including an effort to work with students in the Navajo region, introducing them to radio astronomy. The investigator has developed the Wide-Area Linear Optical Polarimeters (WALOPs), which are based on a novel application of Wollaston prisms. The linear polarization of a star can be measured with a single exposure. This is very important because one needs to measure polarization with accuracy better than 0.1%, and small changes in the atmosphere between successive exposures can cause systematic errors at this level. The team will deploy one of the WALOPs in Crete and the other in South Africa. They will survey the two parts of the celestial sphere that are least contaminated by dust in the Milky Way, around the northern and southern galactic polar caps. This will increase the number of stellar polarization measurements that exist from about 35,000 to over 4 million. They will use the stellar polarization measurements in conjunction with stellar distance measurements to trace the Milky Way magnetic field. The investigators will make major contributions to understanding the structure of the Milky Way’s magnetic fields and determine the effects of Milky Way dust on the polarization signal in the CMB.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.