What the Most Metal-Poor Stars
Tell us about the Early Universe
Anna Frebel
Harvard CfA
The chemical evolution of the Galaxy and the early Universe is a key
topic in modern astrophysics. The most metal-poor Galactic halo stars
are now frequently used in an attempt to reconstruct the onset of the
chemical and dynamical formation processes of the Galaxy. These stars
are an easily-accessible local equivalent of the high-redshift
Universe, and can thus be used to carry out near-field cosmology. The
discovery of two astrophysically very important metal-poor objects has
recently lead to a significant advance in the field. One object is the
most iron-poor star yet found (with [Fe/H]=-5.4). The other star
displays the strongest known overabundances of heavy neutron-capture
elements, such as uranium, and nucleo-chronometry yields a stellar age
of ~13 Gyr. Both stars already serve as benchmark objects for various
theoretical studies with regard to nucleosynthesis processes in the
early Galaxy. I will discuss how the abundance patterns of these and
other metal-poor stars solidify and advance our understanding of the
early Universe, and provide constraints on the nature of the first
stars, as well as their explosion mechanisms and corresponding
supernova nucleosynthesis yields. Large samples of these old objects
are also employed to test theoretical predictions about the formation
of the very first low-mass stars and the lowest observable
metallicity. I will finish the talk with showing brand-new halo-like
abundances of stars in dwarf galaxies which suggests that systems like
these might have been the building blocks of the Milky Way's halo.
Astrophysics Seminar
Markus Böttcher's home page
OU Astronomy and Astrophysics
Department Physics and Astronomy
Ohio University