Primordial Galaxy Star Formation: Exploring the Ultimate Frontier with JWST & ELT

ESA/ESTEC (LEIDEN), THE NETHERLANDS

25–27 August 2026

For more than four decades, the standard scenario of galaxy formation has relied on a two-stage process: the non-dissipative formation of cold (non-colliding) dark matter halos and the dissipative fall of primordial atomic gas at their core (White & Rees 1978, Blumenthal et al. 1984), leading to conditions of temperature and pressure that allowed the first stars to form (e.g. Bromm et al. 1999). The mass distribution of stars formed during the star formation process – as encapsulate by the initial mass function (IMF) – was long thought to be universal, invariant over time and space (e.g., Bastian et al. 2010). Yet, it has now become clear that the IMF can vary substantially depending on the sample of stars one observes and the local physical conditions of star formation (e.g., Conroy & van Dokkum 2012). To quote Hopkins (2018) in his review about the IMF, the question is rather whether the “star formation process itself is universal”.  In particular, it is expected that the formation of the first stars – known as Population III (PopIII) stars – within the pristine regions of the early Universe was supported by mechanisms that were significantly different from those that have governed the formation of subsequent generations of stellar populations, which emerged in a metal-enriched Universe. 

Uncovering how the very first stars ignited and brought light to a dark Universe is thereby literally a burning issue in the study of galaxy formation and evolution. While, a few years ago one could only speculate about the formation of the first stars, extragalactic astronomy has entered a new era, characterised by an access to the epoch of formation of the first stars and galaxies, thanks to the unprecedented sensitivity achieved by the James Webb Space Telescope (JWST; NASA/ESA/CSA). This quest for the first stars will be continued within the next decade with the arrival of the Extremely Large Telescope (ELT). With the deepest infrared observations ever conducted at hand and a handful of robust extremely low-metallicity galaxy candidates identified in the literature, the timing is optimal time to discuss the latest discoveries regarding primordial star formation and the best strategy to leverage follow-up spectroscopic observations with JWST (NIRSpec, MIRI-MRS), ALMA and prepare ELT's forthcoming input.

In this light, the present workshop is dedicated to exploring primordial galaxy star formation, by assembling a small (~20 people) group of both renowned and emerging experts whose record demonstrates an original approach and/or a long-lasting effort to tackle the question, from various perspectives: star formation process, initial mass function, abundance of Population III stars, interplay between supermassive black hole seeds and star formation, from either an observational or a theoretical point of view. The workshop is not specifically meant to showcase new results but rather to foster discussions aiming in particular at 1. taking stock of what we know so far about primordial star formation, 2. comparing state-of-the-art observations and theoretical predictions on all relevant scales and 3. determining the best strategies to leverage the synergies between JWST, ALMA and ELT.