Chemical Signatures of Recent Merger Events in the Outer Halo and the Role of Dwarf Spheroidals in Building the Milky Way

Lai David K, Santa Cruz CA

Investigators

Abstract

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.