Seeking the Lost Interstellar Medium of Red-Sequence Galaxies

凯西·库克西博士被授予NSF天文学和天体物理学博士后奖学金，在麻省理工学院卡夫利天体物理和空间研究所(MKI)开展一项研究和教育计划。在一个典型的星系颜色-星等图中，有两个明显的群体：一个明显的红色序列和一个弥漫的蓝色云。红序星系(RSG)通常具有椭圆形或球状的形态，几乎没有中性星际介质(ISM)，并且不活跃地形成恒星。RSGS往往比组成蓝云的恒星形成的螺旋星系质量更大。制造大质量、“红色和死亡的”椭圆星系的关键一步是停止恒星形成，这将使星系演化成红色序列。关闭恒星形成的可能机制之一是通过星系反馈过程将气体完全从银河系中排出。为了了解RSGs如何失去ISM，库克西博士将进行双管齐下的攻击：(1)用类星体吸收线光谱探测各种红色序列星系的晕，以寻找T~10,000 K气体--被逐出的ISM；(2)表征有气态晕和没有气态晕的星系的年龄、恒星丰度、环境和核活动。对红移为0.25z0.5的50个RSG-类星体对的不同样本将使用稻盛和麦哲伦区域相机与放大器光谱仪和麦哲伦Echellette光谱仪进行观测，这两个互为补充的仪器可以分别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的性质，并应用结果来区分不同的反馈机制。库克西还将设计和教授一门以探究为基础的天文学课程，面向传统上在科学界代表性不足的学生。MKI教育和推广小组将协助招收未得到充分服务的初中生和高中生参加这门课程，该课程将通过麻省理工学院教育研究计划的高中学习计划进行。还将向学生传授当前科学领域的多样性和公平性问题(例如，刻板印象威胁)以及克服这些问题的策略(例如，可塑性思维模式)。

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).