Illuminating the Dark Universe with Radio Observations

我提议开发一项研究计划，对红移21厘米的中性氢气发射进行观测，这将为宇宙历史上未知的领域提供新的线索。氢是宇宙中最丰富的元素，是探索宇宙遥远过去的极其强大的工具。中性氢原子自然发出波长为21厘米的光，由于宇宙的膨胀，这束光被拉伸或发生了红移。通过用无线电频率测量天空，有可能通过选择适当的观测波长来访问宇宙历史的特定时期。 我的研究计划将涉及两个主要主题。第一个目标是探索暗能量的本质，暗能量是宇宙中一种奇怪的成分，导致膨胀速度加快。解决这一挑战的一个很有前途的技术是利用星系21厘米的辐射来制作物质分布的三维地图。物质分布以特定的长度刻度对涟漪(重子声学振荡)进行编码，该刻度可用作绘制宇宙扩张历史和精确定位暗能量引起的增长爆发的“尺子”。进行这些测量需要大型、高灵敏度的射电望远镜阵列，而且这些仪器的设计、实施和操作都面临着独特的挑战。我的计划将涉及为冗余干涉射电望远镜阵列开发新的硬件设计，以及精确描述这些阵列的专门技术。我的研究计划的第二个目标是为未来探索宇宙黑暗时代奠定基础。这一时期发生在宇宙冷却到足以形成中性氢原子之后(大爆炸后约40万年)，到目前为止还没有被探索过，它代表了宇宙学最后的观测前沿之一。从这个时代可以挖掘出潜在的丰富信息，但由于银河系的亮度、电离层效应和地面无线电频率发射，在这些频率上进行相应的21厘米观测格外困难。然而，最近的观察表明，随着现代技术的发展，可以从精心选择的地点进行低频(&lt；30 MHz)测量。我的计划将包括为低频望远镜阵列开发全新的仪器设计，以及为我和我的团队最近安装的低频探路系统进行数据分析。 我的整个计划将是多方面的，将把仪器设计、表征、集成和分析结合在一起。除了提供高影响力的科学，我的项目还将为HQP提供出色的培训，以发展广泛的实验研究和领导技能，这些技能对于开辟宇宙学新的发现空间至关重要。

I propose to develop a research program in observations of redshifted 21-cm emission of neutral hydrogen that will shed new light on uncharted territory in the universe's history. Hydrogen is the most abundant element in the universe and is an extremely powerful tool for probing the universe's distant past. Neutral hydrogen atoms naturally emit light with a wavelength of 21 cm, and this light is stretched or "redshifted" because of the expansion of the universe. By measuring the sky at radio frequencies, it is possible to access specific epochs of the universe's history by selecting the appropriate observational wavelengths. My research program will address two major themes. The first goal is to probe the nature of dark energy, a bizarre component of the universe that is causing the expansion rate to accelerate. A promising technique for tackling this challenge is using 21-cm emission from galaxies to make a three-dimensional map of the distribution of matter. The matter distribution encodes ripples ("baryon acoustic oscillations") with a characteristic length scale that can be used as a "ruler" for charting the expansion history of the universe and pinpointing the growth spurt caused by dark energy. Large, highly sensitive radio telescope arrays are required to make these measurements, and there are unique challenges associated with the design, implementation, and operation of these instruments. My program will involve the development of novel hardware designs for redundant interferometric radio telescope arrays, as well as specialized techniques for precise characterization of these arrays. The second goal of my research program is to lay the groundwork for future explorations of the cosmic dark ages. This epoch, which occurred after the universe cooled sufficiently for neutral hydrogen atoms to form (~400,000 years after the big bang) is unexplored to date and represents one of the final observational frontiers in cosmology. There is a potential wealth of information to be mined from this era, but corresponding 21-cm observations at these frequencies are exceptionally difficult because of the brightness of the Milky Way, ionospheric effects, and terrestrial radio-frequency emission. Nevertheless, recent observations suggest that low-frequency (<30 MHz) measurements may be accessible from carefully selected locations and with modern technological developments. My program will involve the development of radically new instrument designs for low-frequency telescope arrays and data analysis for a low-frequency pathfinder system that my team and I recently installed. My overall program will be multi-faceted and will bring together instrument design, characterization, integration, and analysis. In addition to delivering high-impact science, my program will provide excellent training for HQP to develop a wide range of experimental research and leadership skills that are critical for opening new discovery space in cosmology.