Dr. Sarah Hansen is awarded an NSF Astronomy and Astrophysics Postdoctoral Fellowship to carry out a program of research and education at the University of California-Santa Cruz. Dr. Hansen will utilize new and recent observations of galaxy clusters to address key outstanding issues in galaxy evolution and cosmology. The PI will characterize the population of galaxies in clusters to z~1 identified in a joint optical and Sunyaev-Zeldovich (SZ) survey. She will use the measured distribution of optical properties of these systems to (a) constrain models of galaxy formation and evolution and (b) improve cosmological parameter estimation by decreasing the scatter in the mass-observable relationship. This work will be the first time that the evolution of galaxies in massive dark matter halos has been studied with a sample of clusters derived from an SZ survey.
Dr. Hansen will also partner with the California State Summer School for Mathematics and Science (COSMOS) program to develop a course designed to share the excitement of astrophysical inquiry and research with promising high school students from California. Furthermore, by partnering with the California Teach (CalTeach) program, Dr. Hansen will initiate opportunities for teacher training and professional development relating to astrophysics in the high school science curriculum.
During my fellowship I studied clusters of galaxies to extend our understanding galaxy evolution and to probe the expension history of the universe. My work characterized the types of galaxies found in clusters, and used the optical properties of these cluster members to (a) constrain models of how galaxies evolve in this dense environment and (b) improve cosmological parameter estimation by reducing uncertainty in the key relationship linking observable characteristics of clusters to predictions from cosmological models (ie by decreasing the scatter in mass-richness relationship). For this research I used observational data from large sky surveys to statistically characterize the cluster galaxy population. I compared these results with mock galaxy catalogs derived from cosmological simulations to interpret observations and better constrain models. This work also informs the data analysis pipeline under development for the Dark Energy Survey (DES), the next major optical sky survey. The results of my research are critial to ensuring that the targeted precision and accuracy of cluster cosmology results will be possible with DES data. I have improved verification and validation testing of the DES data reduction pipeline, developed algorithms to make mock galaxy catalogs more closely resemble the observed universe, and improved red galaxy-based cluster richness characterization. These projects all strengthen cosmology and galaxy evolution analysis with optical cluster data. I have also developed and taugh an inquiry-driven study of astrophysics, closely modeled on the authentic research experience, within the high school-level COSMOS program at the University of California Santa Cruz. I bridge this program to education programs preparing high school science educators, enabling future teachers to gain experience in bringing the research process to the classroom. I planned and taught the Summer 2010 and 2011 COSMOS astrophysics courses for 25 high school students from around the state of California (many from under-served school districts), and involved CalTeach educators-in-training and a local public high school teacher in implementing these courses.
