Dynamical Mass and Heating of Galaxy Disks

星系盘的动态质量和加热

• 批准号: 1517006
• 负责人: Matthew Bershady
• 金额: $ 69.37万
• 依托单位: University of Wisconsin-Madison
• 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 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1517006&HistoricalAwards=false
• 关键词: Dynamical; Mass; Heating; Galaxy; Disks

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 the study of the motion and structure of a galaxy's disk system as observed through the action of the stars and gas of the galaxy. This project uncovers the archaeological record of mass-assembly and dynamical evolution of today's galaxy disks, revealed by relations between stellar motions and stellar populations. This basic research project will be conducted at a public University, where advances and discovery are combined with teaching and training to a large and diverse audience. The proposed project broadly disseminates knowledge and achieves scientific and technical literacy in these ways: (1) Research and teaching infrastructure will be enhanced by launching science projects on a new WIYN Observatory instrument. (2) STEM course development on galaxy dynamics and spectrograph instrumentation will intertwine with basic research as part of the PI's on-going faculty duties. (3) Graduate and undergraduate training of the future STEM workforce will include astronomical observations, data analysis, instrument commissioning, data mining, and collaborative research. (4) Educational tools on fiber-optics and their use in society will be developed, implemented, and assessed as part of a public project in our Space Place outreach facility, targeted at school-age students and adults. (5) A four-year lecture series on the Milky Way and external galaxies will be connected to this educational project, presenting expert knowledge on fiber-optic astronomical surveys to the public.The projects's primary objective is to couple the relative amplitude of rotation and velocity dispersion of gas and stars with stellar ages and abundances, used as chronometers, to probe the dynamical heating of disks over the past 4--6 Gyrs. This is analogous to what is being measured with resolved stars in ground-breaking studies of the Milky Way, here albeit more coarsely resolved yet broadly applied to a representative galaxy sample over a wide range in halo mass. This study is leveraged by a new integral-field unit (IFU) on the WIYN 3.5-m telescope and a large IFU survey being undertaken in the fourth generation of the Sloan Digital Sky Survey.A primary outcome of this work will be to answer the question of whether apparent variations in stellar mass-to-light ratios are due to changes in the stellar initial mass function, uncertainties in the late phases of stellar-evolution, or subtleties in the assumed distribution of luminous and dark matter. The approach enables accurate measurements of disk mass by explicitly tying the vertical gradients in disk stellar populations into a self-consistent dynamical model. In so doing, the study determines how recent disk heating-rates depend on galaxy properties and environment, thereby constraining the astrophysical source(s) of this phenomenon. The project calibrates a method for measuring stellar velocity dispersions via the asymmetric drift between gas and stars, a related dynamical phenomenon discovered decades ago in the Milky Way and now measurable in external galaxies. The method will be applied to the current generation of integral-field spectroscopic survey data on nearby galaxies and has application at high redshift. The broader implications of this project include the following: (1) Determining the vertical heating rate of spiral disks using spectrophotometric chronometers is novel and establishes a concrete picture of the stellar density profile in the largest dissipational structures in the universe. (2) Coupling differences between stellar and gas kinematics with stellar population ages provides a new means for estimating dynamical mass and calibrating the mass-to-light ratios of stellar populations. (3) Calibrating mass-to-light ratios places stringent constraints on late phases of stellar evolution, the efficiency with which star-formation locks baryons into stars, and the inner density profiles of dark halos.

天体物理学的一个长期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演化的以及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通过星系恒星和气体的作用观察到的星系盘系统的运动和结构。 该项目揭示了今天星系盘的质量组装和动力学演化的考古记录，揭示了恒星运动和恒星种群之间的关系。 这个基础研究项目将在一所公立大学进行，在那里，进步和发现与教学和培训相结合，面向大量不同的受众。 拟议的项目通过以下方式广泛传播知识并实现科学和技术扫盲：（1）通过启动关于新的WIYN天文台仪器的科学项目，加强研究和教学基础设施。 (2)关于星系动力学和光谱仪仪器的STEM课程开发将与基础研究相结合，作为PI持续教师职责的一部分。(3)未来STEM劳动力的研究生和本科生培训将包括天文观测，数据分析，仪器调试，数据挖掘和合作研究。 (4)关于光纤及其在社会中的使用的教育工具将作为我们的Space Place外展设施的公共项目的一部分开发，实施和评估，针对学龄学生和成年人。 (5)关于银河系和外部星系的四年系列讲座将与这一教育项目相联系，向公众介绍光纤天文观测方面的专业知识，这些项目的主要目标是将气体和恒星的相对旋转幅度和速度分散与恒星年龄和丰度联系起来，用作计时器，以探测过去4- 6 Gyrs期间盘的动态加热。 这类似于在对银河系的突破性研究中用解析恒星测量的情况，虽然这里的解析度更粗，但广泛应用于晕质量范围很广的代表性星系样本。 本研究以WIYN 3.5-m望远镜上的新积分场单元（IFU）和斯隆数字巡天第四代计划中的大规模IFU巡天为基础，主要研究恒星质光比的变化是否是由于恒星初始质量函数的变化、恒星演化后期的不确定性、或假设的发光和暗物质分布的微妙之处。 该方法使盘质量的精确测量明确绑在磁盘恒星种群的垂直梯度到一个自洽的动力学模型。 在这样做的过程中，该研究确定了最近的磁盘加热速率如何取决于星系的性质和环境，从而限制了这种现象的天体物理来源。 该项目校准了一种通过气体和恒星之间的不对称漂移测量恒星速度色散的方法，这是几十年前在银河系发现的一种相关的动力学现象，现在可以在外部星系中测量。 该方法将适用于当前一代的积分场光谱调查数据附近的星系，并在高红移的应用。 该项目的更广泛的影响包括：（1）使用分光光度计测定螺旋盘的垂直加热率是新颖的，并建立了宇宙中最大耗散结构中恒星密度分布的具体图像。 (2)将恒星和气体运动学的差异与恒星布居年龄耦合起来，为估算恒星动力学质量和标定恒星布居的质光比提供了一种新的方法。 (3)校准质光比对恒星演化的后期阶段、恒星形成将重子锁定成恒星的效率以及暗晕的内部密度分布都有严格的限制。