GA-NIFS view of LAP1: Assembly of Pop~III stellar clusters during EoR

LAP1 (Lensed and Pristine 1) is one of the most promising candidates for detecting so-called Pop III stars at z~6.6. This work presents new high-spectral-resolution (R~2700) JWST NIRSpec-IFS observations of the system and a detailed re-analysis of all archival JWST and VLT/MUSE data.

The observations confirm the system's very low metallicity, with 12+log(O/H)=6.5–6.8, corresponding to 1–2% solar metallicity, and a low stellar mass of M* = 10^3–4 Msun, inferred from the non-detection in JWST/NIRCam filter stacks and the Hβ luminosity. The high-resolution IFS data constrain upper limits on the dynamical masses (log10(M*/Msun)) of the A and B components; the 1200 Å constraint leads to an estimated possible stellar-population age range of 2–5 Myr, consistent with the first burst of star formation in a pristine environment.

Based on the system's size (<10 pc) and mass, the authors discuss LAP1 as representing the formation of the first stellar clusters within a larger undetected galaxy, similar to other low-metallicity Pop III candidates in the literature. This strengthens LAP1's importance as a laboratory for studying early Pop III star formation during the Epoch of Reionization.