Silicon overabundance in NGC 1277 provides first chemical link to Population III enrichment in local massive galaxies

NGC 1277, with its 1.2 kpc half-light radius and 1.2e11 solar mass, formed the bulk of its stars at z>2 and experienced minimal subsequent accretion, preserving early nucleosynthetic products. High-resolution spectra show silicon absorption lines far stronger than magnesium features, yielding an Si/Fe enhancement of +1.05 that exceeds predictions from both Kroupa IMF models and conventional supernova yield grids by more than 0.5 dex.

Standard chemical-evolution tracks assume enrichment dominated by 10-40 solar-mass core-collapse events, yet these cannot simultaneously reproduce the observed Si excess while keeping Mg/Fe near +0.36. The data instead align with yields from pair-instability supernovae expected for Population III stars in the 140-260 solar-mass range, whose silicon-rich ejecta would remain undiluted in a system that assembled on timescales shorter than 500 Myr.

This result bridges local relic-galaxy archaeology with JWST findings of unexpectedly rapid stellar-mass buildup at z>8. Because NGC 1277's velocity dispersion and compactness limit late-time gas infall, its abundance pattern functions as a relatively clean fossil record, offering a quantitative benchmark that simulations must now match.

Follow-up integral-field spectroscopy of additional compact relics and direct abundance measurements in lensed z>6 galaxies will test whether the same Si/Mg signature appears universally in the first massive systems.