JWST has revealed a surprising abundance of UV-bright galaxies in the first 500 Myr after the Big Bang. This ‘over-luminous’ population subsides at later epochs, pointing to a different and unique regime of star formation at very early epochs. At the same time, there is evidence for unexpected chemical abundances (‘chemical chaos’), with nitrogen- and even carbon-rich galaxies challenging earlier models of chemical enrichment history of the Universe.
These puzzling abundances may be central to later stages of star formation, because they can affect both stellar evolution, the interstellar medium, and star formation. To underscore the importance of this topic, in the last year alone a number of theories have been proposed, from bursty star formation, to differential element removal by feedback, to fast-rotating stars and massive stars. These findings from high redshift resonate with the peculiar abundances of metal-poor absorbers at intermediate redshifts, and with some local ‘fossils’, such as carbon-enhanced very metal-poor stars in the Milky Way halo and surrounding dwarf galaxies, some of which are thought to be descendants of the First Stars, and nitrogen-rich stars in globular clusters and the field, potentially linked to enrichment by massive stars. Local metal-poor stellar populations might be key to unravelling the mysteries of the distant Universe, lying right at our doorstep. In this focus meeting, we aim to bring together a team with expertise in both stellar and galaxy evolution, and from both the high-redshift and local-universe communities, to discuss the wider implications of these findings, to foster collaboration between different but complementary fields, and to identify what future steps are required to paint a clear picture of this new and unexpected stage of our cosmic history.
Specifically, we aim to address these questions:
1. What stellar-evolutionary channels can explain the observed abundances (at high z and
in local fossils)?
2. What can we learn from local fossils that cannot be addressed at high z (yet)?
3. What is the importance of star clusters in the build up of galaxies at early times?
4. How can we combine information from high redshifts and from local systems?
5. What further observations/models are required to make progress?
