Abstract
Whilst the 2 topics in the title of this talk might seem unrelated, there is in fact an important connection. We have recently published a large study in which we found tentative evidence for a spatially varying fine-structure constant. The measurements are made by comparing the observed wavelengths of atomic transitions seen in high redshift absorbing clouds with the same transitions observed in laboratories on Earth. Atomic isotopes are unresolved in even the best available astronomical data, so previous measurements assume terrestrial isotopic abundances, even though the assumption might introduce systematic effects. We have just finished a re-analysis of the published varying alpha dataset eliminating this assumption, solving explicitly for isotopic ratios of magnesium and find that magnesium isotopes in the early universe are not the same as on Earth - as expected if early chemical enrichment comes from a generation of very massive stars. The implications of this result for varying alpha and for early stellar populations will be discussed.
Coffee and tea will be served 20 minutes prior to the seminar.