Dr. David Lai 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. The prevailing formation theory of large galaxies like the Milky Way is hierarchical assembly of sub-galactic-sized systems. The imprints of this formation mechanism in the Galaxy would be unique abundance patterns in outer-halo, very-metal-poor (VMP) stars compared to nearby-halo VMP stars, an indication that a stellar population exists from recent accretion events. However, a fundamental problem is the lack of dwarf spheroidal (dSph) galaxies having similar metallicity distribution functions (MDF) as the halo.
Dr. Lai will study outer-halo VMP stars and search for these unique abundance patterns by capitalizing on resources newly available for this work: a large, spectroscopically selected sample of VMP candidates from the Sloan Extension for Galactic Understanding and Exploration (SEGUE) survey, and abundance analyses using efficient spectroscopy on the Echellette Spectrograph and Imager (ESI) instrument at Keck Observatory. Dr. Lai will also study MDFs of recently discovered Sloan Digital Sky Survey dSphs using the Low Resolution Imaging Spectrometer (LRIS) instrument at Keck. These are excellent objects for exploring the dSph-halo MDF disagreement.
Dr. Lai will also develop a program with the Center for Adaptive Optics (CfAO) to help increase the number of qualified K-12 science teachers by developing a program that will teach the innovative ideas of inquiry-based learning to pre-service science teachers at the undergraduate level and for those seeking teaching certification.
One of the main outcomes of this project has been finding tantalizing clues into the process that formed the Milky Way. Observations were taken at the Keck Observatory, one of the largest optical telescopes in the world, to observe the composition of very faint and distant stars. By understanding the make-up of stars, it is possible to tease out their origin. In particular it becomes possible to establish their likely progenitors and the general star forming environment from which they were born. In observing these faint and distant stars, a completely unique star was discovered. The origins of this unique star are not clear, but it is an indication that it formed in an unique or rare environment as compared to any other star observed to date. A larger sample of these stars also has begun to show differences in composition with stars much more nearby. Taken together, this is evidence that the Milky Way was formed from the merging of multiple smaller galaxies. This is in analogy with the eventual collision and merging that the Milky Way will have with the Andromeda galaxy in the distant future, creating a new galaxy in the process. This project also involved observations of a dwarf Galaxy, newly discovered in 2006, called Bootes I. One finding shows that the stars in it share characteristics to those in our own Milky Way. This also supports the Milky Way formation scenario of merging systems, with galaxies such as Bootes I having played a potentially important role in this process. The other outcome of this fellowship was to help with the teaching and integration of a workshop comparing approaches in teaching science with a teaching credential program for future public primary school teachers. The activity is aimed at improving science education by teaching that different approaches in the teaching of science need to be implemented for students to be fully engaged and to get the most understanding of the subject. Another outcome from this research grant was helping in the development of a lab activity specifically aimed at non-science majors at the junior college level, many of whom are from backgrounds typically underrepresented in science as a whole.
