Seeking the Lost Interstellar Medium of Red-Sequence Galaxies

Kathy Cooksey博士被授予NSF天文学和天体物理学博士后奖学金，在马萨诸塞州理工学院Kavli天体物理学和空间研究所（MKI）开展研究和教育计划。在一个典型的星系颜色-星等图中，有两个明显的族群：一个明显的红色序列和一个弥漫的蓝色云。红序星系（RSG）通常具有椭圆或球状的形态，几乎没有中性星际介质（ISM），并且没有活跃的恒星形成。RSG往往比构成蓝色星云的恒星形成螺旋星系质量更大。制造巨大的“红色和死亡”椭圆星系的关键一步是停止星星的形成，这使得星系进化到红色序列。其中一个可能的机制，将关闭星星的形成是驱逐气体完全从星系通过星系反馈过程。为了了解RSG如何失去ISM，Cooksey博士将进行双管齐下的攻击：（1）用类星体吸收线光谱学探测各种红色序列星系的晕，以寻找T~ 10，000 K气体-排出的ISM;（2）描述年龄，恒星丰度，环境和星系的核活动，有和没有气体晕。50个红移为0.25z0.5的RSG类星体对的不同样本将用Inamori-Magellan区域照相光谱仪和Magellan Echellette光谱仪进行调查，这两种互补的仪器分别允许对星系和类星体进行有效的调查。分析将包括关联星系和晕气体属性，并应用结果来区分不同的反馈机制。库克西博士还将为传统上在科学领域代表性不足的学生设计和教授一门基于探究的天文学课程。MKI教育和外联小组将协助招募服务不足的初中和高中学生参加这门课程，这门课程将通过麻省理工学院教育研究计划的高中研究计划进行。学生们还将学习有关科学的多样性和公平的当前问题（例如，刻板印象威胁）以及克服它们的策略（例如，可塑性思维）。

Dr. Kathy Cooksey is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at the Massachusetts Institute of Technology Kavli Institute for Astrophysics and Space Research (MKI). In a typical galaxy color-magnitude diagram, there are two clear populations: a distinct red sequence and a diffuse blue cloud. The red-sequence galaxies (RSGs) generally have elliptical or spheroidal morphologies, have little or no neutral interstellar medium (ISM), and are not actively forming stars. RSGs tend to be more massive than the star-forming spiral galaxies that constitute the blue cloud. A crucial step to making massive, "red and dead" elliptical galaxies is to halt star formation, which allows the galaxies to evolve onto the red sequence. One of the likely mechanisms that would shut down star formation is the expulsion of the gas entirely from the galaxy through galactic feedback processes. To understand how RSGs lose their ISM, Dr. Cooksey will conduct a two-pronged attack: (1) probe the halos of a variety of red-sequence galaxies with quasar absorption-line spectroscopy in search of T~10,000 K gas--the expelled ISM; and (2) characterize the ages, stellar abundances, environment, and nuclear activity of the galaxies that do and do not have gaseous halos. A diverse sample of 50 RSG-quasar pairs at redshifts 0.25z0.5 will be surveyed with the Inamori-Magellan Areal Camera & Spectrograph and the Magellan Echellette Spectrograph, two complementary instruments that allow for an efficient survey of the galaxies and quasars, respectively. Analysis will include correlating galaxy and halo-gas properties and applying the results to distinguish between different feedback mechanisms.Dr. Cooksey will also design and teach an inquiry-based astronomy course for students traditionally under-represented in the sciences. The MKI Education and Outreach Group will assist in the recruitment of under-served middle- and high-school students for this course, which will be run through the High School Studies Program of the MIT Educational Studies Program. The students will also be taught about current issues of diversity and equity in the sciences (e.g., stereotype threat) and about strategies to overcome them (e.g., malleable mind-set).