Colloquium on Jan. 9, 2025

Galactic Chemical Evolution and the synthesis of heavy isotopes with a variable Initial Mass Function

Speaker: Eda Gjergo (NJU)

Venue: SWIFAR Building 2111

Time: 16:00 PM, Thursday, Jan. 9, 2025

Abstract:

In this talk, I will introduce Galactic Chemical Evolution (GCE), the field that investigates how chemical elements are produced, distributed, and recycled within the interstellar medium through various astrophysical events and processes. While GCE has achieved many successes, numerous open questions remain. One of the most pressing is the production of isotopes beyond the iron peak. Although slow (s-) and rapid (r-) neutron capture processes are known to synthesize most of these elements, some isotopes are out of reach by either s- or r-process pathways.Furthermore, the dominant astrophysical source of r-process enhancement is still under debate, with conflicting claims in the literature. Neutron star mergers have been confirmed to produce some lighter r-process species, but the rate of past neutron star mergers is inconsistent with the heavy element abundance patterns observed in old, metal-poor stars. An often overlooked bias in r-process studies is the influence of the initial mass function (IMF), which has been recently confirmed to vary with both metallicity and star formation rate. This IMF variation affects the proportion of stars formed within specific mass ranges relative to metallicity, consequently impacting the enrichment rate for potential r-process sites.To address the influence of a variable IMF on r-process enrichment, we have extended our open-source galactic chemical evolution model, GalCEM, to incorporate the integrated galaxy-wide IMF (IGIMF), the most successful and robust variable IMF theory. I will be presenting the results of this extension, discussing how it enhances our understanding of r-process enrichment in different galactic environments.