Thursday, May 5, 2005, Pratt Conference Room at 12:30 pm
Surprises from a new survey of the Solar neighborhood
Dr. Birgitta Nordstrom
(Copenhagen University, Denmark, and Lund University, Sweden)
| Surprises from a new survey of the Solar neighborhood: The metallicity distribution, age-metallicity relation, and age-velocity relations for nearby F and G dwarfs are classical tests of the classical evolution paradigm of gradual enrichment and dynamical heating of the Milky Way disk with time. We have combined 1000+ nights of radial-velocity data from Chile, France, and CfA with new ages, metallicities, and Galactic orbits for over 14,000 nearby F and G dwarfs to reinvestigate these diagnostic diagrams. We find that classical evolution models for the Galactic disk fail every one of these standard tests, but the results show interesting analogies with the metallicity-redshift relations seen in distant QSO absorption line systems. |
Tracking the Footprints of the First Stars
Prof. Johannes Andersen
(Copenhagen University, Denmark, and Nordic Optical Telescope, La Palma)
| The nature of the very first stars in the Universe and their role in enriching the primordial gas and forming the first galaxies are a subject of much current interest. No such star has ever been observed, but the elements produced by the first stars in our own Galaxy are preserved in the most metal-poor stars we can find today. High-resolution spectroscopy with the ESO VLT has been used to study the compositon of such very metal-poor stars in unprecedented detail. The results shed new light on both the structure of the first SNe II, the first synthesis of the heavy elements and the nature of the r-process, mixing processes in bright halo giants, and the early chemical evolution of the Galaxy. |