Sailing to the next safe harbour in our trip to the early Universe: The massive star population of metal-poor galaxies

TL;DR

This paper emphasizes the importance of studying very metal-poor massive stars in the Local Group to better understand the early Universe, highlighting current limitations and proposing future observational advancements.

Contribution

It introduces the need for next-generation panoramic and multi-object spectrographs on large telescopes to systematically study metal-poor massive stars.

Findings

Current observations are limited to small regions due to instrument constraints.

Future facilities will enable comprehensive surveys of metal-poor galaxies.

Such studies will significantly advance understanding of early stellar evolution.

Abstract

Very metal-poor massive stars in the Local Group are our best proxies for the Universe's first stars, making them essential for modeling reionization and early galactic chemical evolution. Studying such stars in our Local Universe is key to extrapolating our knowledge to more distant regions, where individual massive stars cannot be resolved but are dynamically and chemically shaping their environments. The MUSE integral field spectrograph has transformed massive star studies in the Milky Way and Magellanic Clouds, but resolving star-forming galaxies containing very metal-poor stars is at the limit of the current field of view and sensitivity. Therefore, only small dedicated efforts of selected regions are studied, providing us with snapshots of low-metallicity massive stars rather than a comprehensive picture. This scarcity is a major bottleneck for understanding and sufficiently modelling the evolution and feedback of massive stars across cosmic time. We therefore envision a new generation of panoramic integral-field spectrographs and high multiplex multi-object spectrographs mounted on dedicated large optical telescopes. Such facilities will not only allow to resolve very-metal-pool galaxies, but further enable the systematic exploration of the massive stellar content across the entire Local Group, thereby reaching a new era in massive star studies and understanding.