Collaborative Research: Using the Lyman Alpha Forest to Probe the Structure of the Universe

合作研究：利用莱曼阿尔法森林探测宇宙结构

• 批准号: 0098258
• 负责人: Arlin P. Crotts
• 金额: $ 17.94万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-07-01 至 2005-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0098258&HistoricalAwards=false
• 关键词: Collaborative; Research; Using; Lyman; Alpha

AST 0098258Crotts In the last few years, astronomers have shown that supernovae (SN), in distant galaxies are fainter than expected. The obvious explanation is that they are farther away than we had thought. If true, this implies that the expansion of the universe is speeding up. This change in expansion is attributed to a so called "vacuum energy" by theoretical physics. This discovery presents both major new opportunities, and a long list of troubling basic new questions. Up to now Gravity has been the hardest part of physics to understand, in part because it has been described by a single number: the Newtonian gravitational constant G which measures its strength. If the universe is speeding up there must be a second number, which should help us understand gravitational physics. In this way, astronomical observations are redefining our understanding of fundamental physics and the universe as a whole. The goals of this project are to provide an independent check of the claim that 70% of the energy density of the universe is some form of mysterious vacuum energy. Astronomical observations are the only way to explore the vacuum energy experimentally, because the effects are significant only over exceedingly large distances. In particular, this project will provide an independent check of the results from supernovae by using angular size as a distance measure. The amount of clumping of the gas between the galaxies will be measured both along the line of sight, and in angle across the sky. The relationship between the two measures gives the distance and hence the acceleration of the universe. The method is insensitive to changes in the state of the universe over long times. The project is urgent, because the vacuum energy remains an unconfirmed, though very plausible, result, and highly significant, because we will have the sensitivity to decisively rule out the amount of vacuum energy suggested by the supernovae, if none were present. In addition to providing an independent check on the SN decelerating universe measurement, this project will also give improved measurements of the clumping of gas between galaxies at early times. This clumping is believed to have arisen from primordial quantum fluctuations when the universe was young.. These fluctuations have been measured at different epochs, and in different ways. However, the methods used in the present project will give the only measurement of the amount of clumping of matter on galaxy sized scales at early times. These new data and simulations will be compared with theoretical predictions, to act as a check on recent investigations which suggest that our present ideas about the growth of small scale structure in the universe are inadequate. Funding for this project was provided by the NSF program for Extragalactic Astronomy & Cosmology (AST/EXC).***

在过去的几年里，天文学家已经证明，遥远星系中的超新星（SN）比预期的要暗。显而易见的解释是，它们比我们想象的要远。如果这是真的，这意味着宇宙的膨胀正在加速。膨胀的这种变化归因于理论物理学所谓的“真空能”。这一发现既带来了重大的新机遇，也带来了一长串令人不安的基本新问题。到目前为止，引力一直是物理学中最难理解的部分，部分原因是它被描述为一个单一的数字：牛顿引力常数G，它测量它的强度。如果宇宙在加速，那么一定有第二个数字，这应该有助于我们理解引力物理学。通过这种方式，天文观测正在重新定义我们对基础物理学和整个宇宙的理解。这个项目的目标是提供一个独立的检查声称，宇宙的能量密度的70%是某种形式的神秘的真空能量。天文观测是实验探索真空能量的唯一方法，因为只有在非常大的距离上，真空能量的影响才是显著的。 特别是，该项目将通过使用角大小作为距离测量来提供对超新星结果的独立检查。星系之间气体聚集的数量将在沿着视线和天空的角度上测量。这两个测度之间的关系给出了宇宙的距离和加速度。该方法对宇宙状态的长期变化不敏感。这个项目是紧迫的，因为真空能量仍然是一个未经证实的，虽然非常合理的结果，而且非常重要，因为我们将有灵敏度来决定性地排除超新星所暗示的真空能量的数量，如果没有存在的话。除了对SN减速宇宙测量进行独立检查外，该项目还将改进早期星系之间气体聚集的测量。这种聚集被认为是在宇宙年轻时由原始量子波动引起的。这些波动在不同的时期以不同的方式被测量。 然而，本项目中使用的方法将给出早期星系大小尺度上物质聚集量的唯一测量。这些新的数据和模拟将与理论预测进行比较，以检查最近的调查，这些调查表明我们目前关于宇宙中小尺度结构生长的想法是不够的。该项目的资金由美国国家科学基金会的河外天文宇宙学计划（AST/EXC）提供。