The challenges of identifying Population III stars in the early Universe
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 524:1 (2023) 351-360
Abstract:
The recent launch of JWST has enabled the exciting prospect of detecting the first generation of metal-free, Population III (Pop. III) stars. Determining characteristics that robustly signify Pop. III stars against other possible contaminants represents a key challenge. To this end, we run high-resolution (sub-pc) cosmological radiation hydrodynamics simulations of the region around a dwarf galaxy at z ≥ 10 to predict the emission line signatures of the Pop. III/Pop. II transition. We show that the absence of metal emission lines is a poor diagnostic of Pop. III stars because metal-enriched galaxies can maintain low [O iii] 5007 Å that may be undetectable due to sensitivity limits. Combining spectral hardness probes (e.g. He ii 1640 Å/H α) with metallicity diagnostics is more likely to probe metal-free stars, although contamination from Wolf-Rayet stars, X-ray binaries, or black holes may be important. The hard emission from Pop. III galaxies fades fast due to the short stellar lifetimes of massive stars, which could further inhibit detection. Pop. III stars may be identifiable after they evolve off the main sequence due to the cooling radiation from nebular gas or a supernova remnant; however, these signatures are also short-lived (i.e. few Myr). Contaminants including flickering black holes might confuse this diagnostic. While JWST will provide a unique opportunity to spectroscopically probe the nature of the earliest galaxies, both the short time-scales associated with pristine systems and ambiguities in interpreting emission lines may hinder progress. Special care will be needed before claiming the discovery of systems with pure Pop. III stars.Nitrogen enhancements 440 Myr after the big bang: supersolar N/O, a tidal disruption event, or a dense stellar cluster in GN-z11?
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 523:3 (2023) 3516-3525
Simulating the diversity of shapes of the Lyman-α line
Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 523:3 (2023) 3749-3772
A novel approach to correcting Te-based mass–metallicity relations
Monthly Notices of the Royal Astronomical Society: Letters Oxford University Press (OUP) 522:1 (2023) l89-l94
Evidence for a Low Lyman Continuum Escape Fraction in Three Massive, Ultraviolet-bright Galaxies at z > 7
The Astrophysical Journal American Astronomical Society 944:1 (2023) 61