Dr. Gail Zasowski is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at The Ohio State University (OSU). One of the greatest unresolved puzzles of our Milky Way Galaxy (MW) is the nature of the long central bar: its structure, dynamics, and stellar chemical composition. The bar is expected to have a significant impact on mass and abundance distributions in the inner Galaxy, which are used to characterize the MW's global properties and their relation to those of other galaxies. This characterization is crucial for understanding not only the MW but also general galactic evolution because the proximity and accessibility of the MW makes it the most powerful resource that investigators have to develop models of galaxy formation and aging. Unfortunately, a thorough understanding of the MW's fundamental properties has been precluded as its inner regions, where most of the stellar mass is located, are behind the thick dust of the midplane. New infrared (IR) data from multiple photometric and spectroscopic surveys are providing a way to probe these inner regions at a level never before possible. The fellow plans a comprehensive analysis of the inner MW that focuses on the spatial, dynamical, and chemical properties of the influential but poorly-understood long bar. This project will take advantage of the unprecedented availability of both photometric and spectroscopic infrared observations of the inner MW midplane, including unique high resolution IR spectra from the Sloan Digital Sky Survey III's Apache Point Observatory Galactic Evolution Experiment (APOGEE).
The fellow will combine near- and mid-IR photometry to produce an extinction-corrected catalogue of stars spanning the long bar and outer bulge, and she will use this catalogue to make the first stellar density map of these regions that is capable of measuring the long bar's position, axial ratios, and structural coherence. She will collect radial velocities with APOGEE for a large sample of red clump (RC) giants in the long bar and compare them to kinematical predictions from N-body and stellar dynamics models to measure the bar's systematic velocity, dispersion, and dynamical coherence. Of particular interest are the kinematics of the "transition regions" where resonances influence the bar-bulge and bar-disk relationships. Finally, the fellow will use the APOGEE-derived metallicities and abundances of the RC sample to measure the metallicity distribution along the bar, including the presence of multiple stellar populations. The result will be a complete picture of the long bar's spatial, dynamical, and chemical distributions, which can be used to establish the bar's properties compared to external galactic bars, along with its stellar properties and mixing efficiency.
The broader impacts of this project include a significant educational component. The fellow will leverage OSU's partnership with Ohio's 4-H program to demonstrate to children and the general public that science and scientific inquiry are fun, relevant to their lives, and perhaps most importantly, accessible to all. In partnership with the Ohio 4-H state office, the fellow will contribute to two projects teaching scientific concepts through interactive activities, with an emphasis on those that can be easily done in the home. First, she will develop astronomy-themed activities for an annual summer Space Camp targeted at middle-school students. Second, she will combine astronomy-themed activities with suitable background information and evaluation metrics into a Space Science Project Book for 4-H's Project Book series, which encourages students to select, design, and evaluate their own learning experiences beyond the classroom. The close association of 4-H with rural and often economically disadvantaged schools means that the materials that she develops will impact the scientific literacy of these underserved communities.
