A population study on the effect of metallicity on ZAMS to the merger

The formation channels of compact object binaries are crucial for interpreting gravitational wave observations and enhancing early multi-messenger alerts. Despite the key role of stellar metallicity in progenitor evolution, many models assume a uniform value for all stars in a cluster. In this study, we investigate the impact of a heterogeneous stellar metallicity distribution on the formation of compact object binaries and their resulting gravitational wave signatures. We extend the COSMIC binary population synthesis code to incorporate a fiducial mass-redshift-metallicity relation for individual Zero-Age Main Sequence stars of a stellar cluster. Focusing on low-metallicity environments at redshift $z \approx 4$, we analyse the gravitational-wave signals from binary black holes and black hole-neutron star systems in the sub-hertz regime. The resulting binary black holes have total masses from $8$-$86\,M_\odot$, while black hole--neutron star systems range from $6$-$31\,M_\odot$. We assess the detectability of the characteristic strains against the sensitivity curves of planned sub-hertz observatories.