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 0.25 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). The "circum-galactic medium" (CGM) is the interface between the galaxy's interstellar gas, from which it forms stars, and the diffuse intergalactic medium. My research focuses on the evolution of heavy elements, or metals, in the CGM, as observed in absorption. From metal absorption-line systems, we learn about the elemental abundances and spatial distribution of the absorbing gas and the spectral characteristics of the ionizing radiation. These properties are all affected by galactic feedback processes, which can be probed across cosmic time with quasar absorption-line (QAL) spectroscopy. I combine QAL spectroscopy with galaxy surveys to directly connect metal-line systems with their host galaxies. For the original project of my NSF Fellowship, I am seeking the ejected interstellar gas from "red and dead" galaxies, in order to understand what caused these massive galaxies to stop forming stars. I have observed a diverse sample of galaxies and their background quasars through MIT's time on the Magellan/Clay 6.5-m Telescope at Las Campanas Observatory in Chile. I aim to characterize galaxies that do and do not have warm halo gas and directly compare galaxy and absorber properties, where absorption is detected. Preliminary results indicate that the cool gas covering fraction increases for lower-mass galaxy halos, which support the trend detected previously. With large QAL surveys, I observe the chemical evolution of the CGM over cosmic time, from a billion years after the Big Bang to the present epoch. The NSF Fellowship brought me to the MIT Kavli Institute, where my sponsoring scientist and I decided to survey the large public Sloan Digital Sky Survey (SDSS) for common, strong metal-line systems. We vastly improved the statistics by identifying over 15,000 triply-ionized carbon absorption systems (see Primary Image). Such absorbers are rare in traditional (small) surveys (see Image 2). I have made all data, results, and codes available via http://igmabsorbers.info, for use by any researcher or citizen scientist. The NSF Fellowships also enabled me to develop my teaching and mentoring skills. In my first year, I taught a section of MIT's introductory physics course, which is required for graduation, and it is rare for a postdoctoral researcher to teach such a course at MIT. The course was the "technology-enabled active learning" version, which has an innovative design focused on students learning problem-solving skills by solving problems, in and out of the classroom. This was my first opportunity to teach a rigorous science course to undergraduates. My broader impacts focus for my last two years was mentoring an undergraduate researcher. I solicited applicaitons from a diverse student body, by advertising through MIT's Undergraduate Research Opportunity Program, Society of Physics Students, Women in Physics, and the Office of Minority Education (OME). The student I ultimately selected was an aeronautics/astronautics engineering major, who read my ad through the OME mailing list. The project was his first research experience, and it was a complete one. He began by visually verifying over 60,000 singly ionized magnesium (MgII) systems and ended with a publication in The Astrophysical Journal. Image 3 is excerpted from this article, Seyffert et al. (2013). This research experience has contributed to the student applying to graduate schools. My research, education and outreach efforts, supported by the NSF Fellowship, contributed---significantly, in my opinion---to my landing an assistant professorship at the University of Hawai'i at Hilo. The appointment is exceedingly well suited to my skills and interests, and I am extremely grateful to the NSF and the U.S. taxpayer for helping me acheive the career I have aimed for since my sophomore year of high school. This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.Project Report
