A Complete Census of the Quasar Population in the Large Survey Era

大巡天时代类星体种群的全面普查

• 批准号: 1515115
• 负责人: Xiaohui Fan
• 金额: $ 26.52万
• 依托单位: University of Arizona
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1515115&HistoricalAwards=false
• 关键词: Complete; Census; Quasar; Population; Large

A longstanding problem in astrophysics is to understand how galaxies form and develop throughout their lifetimes. Such understanding is necessary to uncover how our Universe evolved and to gain insight into the origin of our own Milky Way Galaxy. One important aspect of understanding galaxy formation and evolution is to study supermassive black holes (BHs) at the centers of massive galaxies. These BHs light up as quasars during the relatively brief phases when the BHs accumulate most of their mass through accretion. Over the past half-century, considerable effort has been devoted to capturing these accretion spurts through surveys at optical wavelengths. In general, these surveys have been limited to the most luminous sources, or small numbers within deep fields; however, quasar observations are undergoing an exponential leap in depth and breadth enabled by new and upcoming surveys. The Baryon Oscillation Spectroscopic Survey of the Sloan Digital Sky Survey III (SDSS-III/BOSS) final data release will include about 160,000 quasars at redshifts around 2--3, and its successor, the SDSS-IV/eBOSS, will obtain spectra of over 600,000 quasars at redshifts around 1--2. The investigators will complement the quasar samples from these cosmology surveys with their own high redshift programs to form a complete picture of the evolution of faint quasars from optical surveys. The investigators will integrate the science program into a tiered outreach program at Pima Community College, a Hispanic-Serving Institution located in Tucson. The outreach program includes (1) public lectures at the East Campus, a region not reached by The University of Arizona programs, (2) lectures to Astronomy 101 students at Pima integrating an overview of Active Galactic Nuclei into the regular curriculum, and (3) engagement of a small number of Pima students in the research program itself by teaching the basics of quasar spectroscopy and including the students in the eBOSS program to visually inspect quasar spectra.More technically, exploring this method in the regime of sparse data (an important precursor for LSST), the team will utilize Large Synoptic Survey Telescope (LSST) reductions of SDSS imaging data to identify about 400 quasars at redshifts around z = 4 through variability selection. Finally, the team will use deep CFHT imaging to reach faint quasars (i_AB = 24) at redshift around z = 5. Together, these data will probe several magnitudes below the break luminosity over a wide redshift range and will reach nearly all objects classifiable as quasars over 5 Gyr of cosmic evolution, including the crucial epoch when both star formation and quasar activity peak.Leveraging massive spectroscopic surveys as well as separate observations with large telescopes, the team will complete the census of the faint end of the quasar luminosity function to redshift around z = 5 and obtain new measurements of high-z clustering, thereby providing strong constraints for models of quasar lifetimes and feedback physics. These measurements will also provide strong constraints on the quasar ionizing background during the epoch of He II reionization. Finally, a key aspect of the project is to develop tools needed for an era when quasar surveys will be dominated by systematics rather than by statistics. The team will accomplish this by building models for quasar properties constrained by existing observations but which provide useful projections for future surveys. These models will be used to guide target selection for spectroscopic efforts, identify quasars from photometric data, and train photometric redshift estimation; furthermore, they will provide insight into intrinsic quasar properties, such as continuum and dust extinction.

天体物理学中一个长期存在的问题是了解星系在其一生中是如何形成和发展的。这样的理解对于揭示我们的宇宙是如何进化的，并深入了解我们银河系的起源是必要的。了解星系形成和演化的一个重要方面是研究大质量星系中心的超大质量黑洞（BHs）。在相对短暂的阶段，这些黑洞通过吸积积累了大部分质量，从而成为类星体。在过去的半个世纪里，人们花了相当大的努力，通过光学波长的调查来捕捉这些吸积爆发。一般来说，这些调查仅限于最明亮的光源，或深场内的少量光源；然而，由于新的和即将到来的调查，类星体观测正在经历深度和广度的指数级飞跃。斯隆数字巡天III （SDSS-III/BOSS）的重子振荡光谱调查最终数据发布将包括大约16万个红移在2- 3附近的类星体，其继任者SDSS-IV/eBOSS将获得超过60万个红移在1- 2附近的类星体的光谱。研究人员将用他们自己的高红移程序来补充这些宇宙学调查的类星体样本，以形成光学调查中微弱类星体演化的完整图景。调查人员将把科学项目整合到皮马社区学院的一个分层扩展项目中，这是一所位于图森的西班牙裔服务机构。外展计划包括(1)在亚利桑那大学项目未涉及的东校区进行公开讲座；(2)在皮马大学为天文学101学生提供讲座，将活动星系核的概述纳入常规课程；(3)通过教授类星体光谱的基础知识，让少数皮马学生参与研究计划，并让学生参加eBOSS项目，以直观地检查类星体光谱。更技术性的是，在稀疏数据（LSST的重要前身）的范围内探索这种方法，该团队将利用大型天气巡天望远镜（LSST）对SDSS成像数据的减少，通过变异性选择在z = 4附近的红移处识别大约400个类星体。最后，研究小组将使用深CFHT成像来到达红移z = 5附近的暗类星体（i_AB = 24）。总的来说，这些数据将在一个很宽的红移范围内探测到在断裂光度以下的几个星等，并将探测到在宇宙演化的5gyr范围内几乎所有可归类为类星体的物体，包括恒星形成和类星体活动达到顶峰的关键时期。利用大规模的光谱调查以及大型望远镜的单独观测，该团队将完成类星体亮度函数在z = 5附近红移的微弱末端的普查，并获得高z群集的新测量，从而为类星体寿命模型和反馈物理提供强有力的约束。这些测量结果也将对He II再电离时期的类星体电离背景提供强有力的约束。最后，该项目的一个关键方面是开发类星体调查将由系统学而不是统计学主导的时代所需的工具。该团队将通过建立类星体属性模型来实现这一目标，这些模型受到现有观测结果的限制，但为未来的调查提供了有用的预测。这些模型将用于指导光谱工作的目标选择，从光度数据中识别类星体，并训练光度红移估计；此外，它们将提供对类星体固有特性的深入了解，如连续介质和尘埃消光。