Collaborative Research: Towards the Edge of the Milky Way. The First Contiguous Spectroscopic Survey of the True Outer Halo.

合作研究：走向银河系边缘。

• 批准号: 1212000
• 负责人: Constance Rockosi
• 金额: $ 19.59万
• 依托单位: University of California-Santa Cruz
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2017-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1212000&HistoricalAwards=false
• 关键词: Collaborative; Research; Towards; Edge; Milky

The long dynamical times and radial extent of our stellar halo preserves a chance to trace the history of mass assembly of both the stellar and dark matter components of our Galaxy. Most of what we know about the outer halo is learned from stars that happen to pass nearby. If the outer halo is, as we expect, dynamically young and not well mixed, the motion of such stars may not tell the full story of the recent accretion history of the Galaxy. Dr. Rockosi (at the University of California Santa Cruz) and Dr. Morrison (at Case Western Reserve University)work on a spectroscopic survey of red giant branch stars in the outer halo, done as part of the Baryon Oscillation Spectroscopic Survey (BOSS). This is the dark time survey in the Sloan Digital Sky Survey (SDSS)-III project. The BOSS spectrograph improvements and large area coverage of an area of about 10,000 square degrees allow a contiguous survey of the outer reaches of our Galaxy. The complete sample will provide kinematics, metallicities, and alpha element to iron abundance ratios for approximately 1000 stars with a median distance of 50 kpc, providing a true outer halo sample. The alpha elements such as O, Mg, and Si are mainly produced in supernovae and trace the chemical evolution of the halo. The outer halo sample will be used to measure the halo stellar radial density profile, metallicity and alpha element abundance gradients to beyond 100 kpc from the center of the Galaxy, as well as identify and characterize substructure in stellar density, kinematics and chemical abundance. From this we can learn the fractional contribution of stellar accretion to the outer halo, as well as the mass and orbit distributions and star formation histories of the halo progenitors. Comparison of these measurements in the outer halo to existing measurements in the surviving dwarf spheroidal galaxies and in the inner halo can be used to infer the mass accretion history and stellar population evolution of our Galaxy and its progenitors through time. All SDSS data become public in a timely manner, giving a rich and in many ways still unexplored resource to astronomers. The principal investigators have led the stellar surveys in the SDSS projects from proposals through data releases. All have been actively involved for the past six years in the calibrations needed before these data can be used reliably for stars, which included improving the flux calibration of the SDSS spectra, to tests of the stellar parameters pipeline to the painstaking observation and analysis of well-studied open and globular clusters. Minority students remain a small proportion of graduating PhDs. Case astronomy is partnering with the very successful Fisk/Vanderbilt Masters Bridge Program for minorities so that their graduates can enter the Case Western Reserve University astronomy PhD program in the same way that they currently enter the Vanderbilt PhD program; effectively as third-year graduate students. The Case program for Women in Science and Engineering (co-founded by the PI) is now in its ninth year of encouraging women undergraduates to stay in science. Dr. Rockosi leads many projects to develop facility instrumentation at Keck and Lick Observatory. These instruments are available via public access to Keck, and the Lick Observatory projects provide a technology development platform for adaptive optics and other instrumentation research. Dr. Rockosi and her research group participate in the Santa Cruz Institute for Science and Engineering Educators, which introduces graduate students and postdocs to inquiry-based learning techniques while running workshops designed to encourage underrepresented minority students to go on for advanced degrees in STEM fields. Approximately 75% of the undergraduate participants in this program are women or under-represented minorities.

我们的恒星晕的长动力学时间和径向范围保留了一个机会，以跟踪我们银河系的恒星和暗物质组件的质量组装的历史。我们对外晕的大部分了解都是从碰巧经过附近的恒星那里学到的。如果外晕像我们预期的那样，在动力学上是年轻的，并且没有很好地混合，那么这些恒星的运动可能无法讲述银河系最近吸积历史的全部故事。Rockosi博士（在加州大学圣克鲁斯）和莫里森博士（在凯斯西储大学）从事外晕红巨星分支恒星的光谱调查，作为重子振荡光谱调查（BOSS）的一部分。Sloan Digital Sky Survey（SDSS）-III项目中的暗时巡天。BOSS摄谱仪的改进和大约10，000平方度的大面积覆盖范围允许对我们银河系的外部进行连续调查。完整的样本将提供大约1000颗恒星的运动学，金属丰度和α元素与铁的丰度比，中值距离为50 kpc，提供真正的外晕样本。α元素如O、Mg和Si主要在超新星中产生，并追踪晕的化学演化。外晕样品将用于测量从银河系中心到100千秒差距以外的晕恒星径向密度分布、金属丰度和阿尔法元素丰度梯度，以及确定和表征恒星密度、运动学和化学丰度的亚结构。从中我们可以了解恒星吸积对外晕的贡献，以及晕祖星的质量和轨道分布以及星星的形成历史。这些测量结果的比较，在幸存的矮球状星系和内晕的外晕现有的测量可以用来推断质量吸积的历史和恒星的人口演化我们的银河系及其祖先通过时间。所有SDSS数据都及时公开，为天文学家提供了丰富的，在许多方面尚未开发的资源。主要研究人员领导了SDSS项目中的恒星调查，从提案到数据发布。在过去的六年里，所有人都积极参与了在这些数据可以可靠地用于恒星之前所需的校准工作，其中包括改进SDSS光谱的通量校准，测试恒星参数管道，对经过充分研究的疏散星团和球状星团进行艰苦的观测和分析。少数民族学生在博士毕业生中所占比例仍然很小。凯斯天文学与非常成功的菲斯克/范德比尔特硕士桥梁计划合作，使他们的毕业生可以进入凯斯西储大学天文学博士课程，就像他们目前进入范德比尔特博士课程一样;有效地作为三年级的研究生。科学和工程领域妇女案例方案（由PI共同创立）现在已经是鼓励女大学生留在科学领域的第九个年头。Rockosi博士领导了许多项目，在Keck和Lick天文台开发设施仪器。这些仪器可通过公众访问凯克，利克天文台项目提供了一个技术开发平台，自适应光学和其他仪器的研究。Rockosi博士和她的研究小组参加了圣克鲁斯科学与工程教育家研究所，该研究所向研究生和博士后介绍了基于探究的学习技术，同时举办研讨会，旨在鼓励代表性不足的少数民族学生继续攻读STEM领域的高级学位。大约75%的本科生参与者是女性或代表性不足的少数民族。