Probing the Epoch of Reionization with the Brightest High-Redshift Quasars

用最亮的高红移类星体探索再电离时代

• 批准号: 1615814
• 负责人: George Becker
• 金额: $ 37.96万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1615814&HistoricalAwards=false
• 关键词: Probing; Epoch; Reionization; Brightest; Redshift

An important period in the early history of the universe is the so-called "epoch of reionization". This is a period a few hundred million years after the Big Bang during which all of the atomic Hydrogen gas in the universe was ionized by newly formed massive stars. These were the first stars to form in the universe. Understanding this early period is one of the main goals of astrophysics. This is because properties of the unverse (and the objects causing the ionization) carry implications for models and simulations of how galaxies form and the physics of the matter being ionized (the intergalactic medium or IGM). This project will shed new light on reionization and high-redshift galaxies by observing the IGM after the epoch of reionization. At these times, the IGM contains a large amount of information on when and how reionization occurred. Fortunately, in the past year a set of "ultra-bright" quasars have been discovered that are much brighter than previously known quasars at similar distances. The PI and his team will make entirely new or greatly improved measurements of three aspects of the post-reionization IGM: (i) the smoothing of baryons in the IGM due to heating during reionization, (ii) the thermal changes of the IGM due to cool-down following reionization, and (iii) the most sensitive study to date of the enrichment of elements heavier than helium of gas in galaxies from this period. This latter measurement will aid in the understanding of early-period star formation.Education efforts supported by this project will reach young children in predominantly Hispanic, low-income communities. The PI and graduate student funded by this grant will help to develop, manage, and perform astronomy-themed workshops designed to promote STEM education in kindergarten, first, and second-grade students. The workshops will address California's Common Core State Standards for science, and target underserved communities in Riverside and surrounding areas. Workshop themes will include Touching the Universe, The Spiral Universe, Constellations Everywhere, and Smells of the Universe. This project clearly relates to NSF's mission to promote the progress of science. In addition, the "Broader Impact" portion of the project does this, and advances the national health, prosperity and welfare by helping to develop interest in, and educating, STEM activities among the next generation of diverse individuals.Understanding the epoch of reionization remains one of the forefront goals of astrophysics. Along with being the last global phase change of the Universe, reionization carries key implications for models of galaxy formation and the physics of the intergalactic medium (IGM). Over the past several years, notable advances have been made through observations of high-redshift galaxies, quasars, the cosmic microwave background, and other probes. Currently, however, the combined constraints on when reionization occurred remain relatively weak, with the bulk of observations being consistent with reionization ending either relatively late (z~6-7) or significantly earlier (z~8-9).Motivated by these new objects, the PI and his team will make entirely new or greatly improved measurements of three aspects of the post-reionization IGM and galaxy-IGM interface: (i) Measuring the Jeans smoothing of the IGM at z~5 will reveal how much energy has been injected at higher redshifts via photo-heating, and hence when reionization occurred (more total heating = earlier reionization). This measurement will constrain the characteristic redshift of reionization to within Deltazreion=+/-0.7, or a factor of two better than current CMB constraints. (ii) Measuring the temperature of the IGM out to the highest redshifts ever (z=5.7) will determine whether the IGM is still warm at that epoch from having recently been reionized. Alternatively, an IGM that has already cooled by z~5.5 will imply that reionization largely occurred at z7.5. (iii) Finally, the survey for CIV at z~5 will be sensitive to metals down to the cosmic mean density, probing a factor of six more volume than any other direct survey at any redshift. This will reveal, for the first time, the full extent to which reionization-era galaxies enriched their surroundings via galactic winds. Searching for weak O I systems at z~6 also will establish whether the drop in C IV with redshift at z5 is due to a decline in metallicity or evolution of the UV background.

宇宙早期历史的一个重要时期是所谓的“电离时代”。 这是大爆炸发生几亿年后的一个时期，在此期间，宇宙中的所有原子氢气都被新形成的大型恒星电离。 这些是在宇宙中首批形成的恒星。 理解这一早期是天体物理学的主要目标之一。 这是因为非反面的特性（以及导致电离的对象）对模型的影响以及模型的含义，并模拟了星系的形成方式以及物理被电离的物理学（播层间介质或IgM）。 该项目将通过观察电离时期的IGM来展示有关电离和高红移星系的新启示。 在这些时候，IGM包含大量有关何时以及如何进行回离的信息。幸运的是，在过去的一年中，已经发现了一套“超亮”的类星体，它们比以前在类似距离的现金类品牌要明亮得多。 PI和他的团队将对静电后IGM的三个方面进行全新或大大改进的测量：（i）由于恢复原动的速度，（iiiii and e e e element of earvier of earvier of See ver of See ver of See ver of See ver of See ver of See ver of See ver of See ver，iigm在恢复过程中的供热造成的IGM的平滑率平滑，（ii）IgM的热变化。 后一种测量将有助于理解早期的星星形成。该项目支持的教育工作将吸引主要是西班牙裔，低收入社区的幼儿。由该赠款资助的PI和研究生将有助于开发，管理和执行以天文学为主题的讲习班，旨在促进幼儿园，一年级和二年级学生的STEM教育。该研讨会将解决加利福尼亚州的普通核心科学标准，并针对河滨和周边地区服务不足的社区。研讨会主题将包括接触宇宙，螺旋宇宙，到处都是星座以及宇宙的气味。该项目显然与NSF促进科学进步的使命有关。 此外，该项目的“更广泛的影响”部分是这样做的，并通过帮助建立对下一代不同个人的兴趣和教育的STEM活动来促进国家健康，繁荣和福利，这是天体物理学的前沿目标之一。除了是宇宙的最后一个全球阶段变化外，电离还对星系形成模型和播层间培养基（IGM）的物理具有关键意义。在过去的几年中，通过观察高红移星系，类星体，宇宙微波背景和其他探针取得了显着进步。然而，目前，对何时进行恢复的综合限制仍然相对较弱，大多数观察结果与反应结束相对较晚（z〜6-7）或更早地结束（z〜8-9）（z〜8-9）。这些新物体对这些新物体进行动力，PI和他的团队将完全或很大程度上改进了三个方面的相互作用，并将三个方面的相互作用。测量Z〜5时IgM的牛仔裤平滑，将揭示通过照相加热在较高红移处注入多少能量，因此，当进行回报时（更多的总加热=早期的恢复）。该测量将将电离的特征红移限制为在deltazreion =+/ - 0.7内，或比当前CMB约束的两个因子。 （ii）将IgM的温度测量到有史以来最高的红移（Z = 5.7）将确定在该时期的IgM是否仍然温暖，以免最近被电离。或者，已经通过Z〜5.5冷却的IgM意味着Z7.5的电源很大程度上发生。 （iii）最后，Z〜5的CIV调查将对金属敏感到宇宙平均密度，探测比任何红移时的任何其他直接调查都要高6倍。这将首次揭示电离时代的星系通过银河风丰富周围环境的全部程度。在Z〜6处搜索弱的O I系统还将确定在Z5处红移的C IV下降是由于紫外线背景的金属性或演变的下降。

项目成果

Determining the Nature of Late Gunn–Peterson Troughs with Galaxy Surveys

• DOI: 10.3847/1538-4357/aac2d6
• 发表时间: 2017-08
• 期刊: The Astrophysical Journal
• 作者: F. Davies;G. Becker;S. Furlanetto