VU Physics and Astronomy Colloquium

Friday, Nov. 4. Refreshments in NSC Planetarium at 3:05 PM, followed by the colloquiuim in 221 at 3:30 PM.

Nucleosynthesis of Trans-Iron Elements Through the Eyes of Nebular Spectroscopy

Dr. Nicholas Sterling, Dept. of Physics & Astronomy, Michigan State University

The production and chemical evolution of neutron(n)-capture elements (atomic number Z > 30) in the Universe has historically been investigated via stellar spectroscopy. However, in the last decade it has become apparent that nebular spectroscopy is a potentially powerful new tool for understanding the origins and nucleosynthesis of heavy elements. In this time, trans-iron element emission lines have been detected in a large number (∼100) of planetary nebulae, as well as in H II regions and the interstellar medium of other galaxies. Nebular spectroscopy provides access to several elements that cannot be detected in stars, and to classes of stars and stages of stellar evolution that are extremely challenging to probe via stellar spectroscopy. I will discuss observational studies of n-capture element emission lines, with an emphasis on their detection in planetary nebulae and implications for heavy element and carbon production in low-mass stars.

The recent nature of this field presents unique complications in terms of interpreting trans-iron element spectroscopic features. Foremost among these challenges is the lack of atomic data for n-capture elements, particularly for processes that affect their ionization equilibrium in astrophysical nebulae, which severely inhibits accurate abundance determinations. Any progress toward transforming nebular spectroscopy into an effective tool for understanding the abundances and nucleosynthesis of trans-iron elements therefore requires a multi-disciplinary approach. I will discuss a laboratory astrophysics program utilizing both theoretical and experimental methods to determine atomic data for detected n-capture elements, and their application to observational data for abundance determinations.