Astro Seminar Series - VIA ZOOM

Thursday, June 11, 2020 11:30 am - 11:30 am EDT (GMT -04:00)

David Weinberg
David Weinberg is a Distinguished University Professor and Chair of the Department of Astronomy at Ohio State University.  His research interests include large scale structure, weak lensing, and observational constraints on cosmic acceleration; the physics of galaxy formation, the intergalactic medium, and circumgalactic medium; and the chemical evolution of the Milky Way.  Prior to joining the Ohio State faculty, he received his PhD from Princeton University (1989) and held postdoctoral positions at Cambridge University, U.C. Berkeley, and the Institute for Advanced Study.  He has been a member of the Sloan Digital Sky Survey (SDSS) since 1992, including serving as Spokesperson of SDSS-II and Project Scientist of SDSS-III.  He has collaborated with artist Josiah McElheny on the design of cosmological sculptures that illustrate the evolution of cosmic structure and the possibility of island universes in an inflationary sea.

Title and Astract for David's talk:

Decoding Chemical Evolution and Nucleosynthesis

I will discuss insights from analytic and numerical models of galactic chemical evolution and observations of Milky Way elemental abundances from the SDSS APOGEE survey.  Under generic model assumptions, abundances and abundance ratios approach an equilibrium in which element production from nucleosynthesis is balanced by element depletion from star formation and outflows. Reproducing solar abundances requires outflows with mass-loading factors of 1-3, but one can evade this conclusion by assuming low stellar yields or metal-enhanced winds; the high observed deuterium abundance of the local ISM argues against these alternatives and in favor of outflows. Starbursts or other sudden transitions can produce temporary boosts in alpha-to-iron ratios, and other surprising behavior such as backward evolution of a stellar population from high metallicity to low metallicity.  APOGEE observations show that the distributions of stars in (alpha,iron,age)-space change steadily across the Milky Way disk.  Given these distributions, the behavior of other APOGEE abundance ratios can be explained by changes in the ratio of core collapse to Type Ia supernova enrichment.  The separability of "multi-element cartography" offers a route to empirically constraining supernova yields in a way that is insensitive to uncertainties in other aspects of chemical evolution.

Would you like to join this Zoom seminar?  Please email Donna Hayes.