FIG 1: more than an order of magnitude in scatter in the R2 ratio, suggesting there is significant diversity in the ISM conditions of galaxies within this sample.

Low metallicities but still a range and not extremely metal poor even at highest z (<0.1Zsun). 

Some overlap with the region inhabited by typical z ∼ 2 MOSDEF galaxies. These may represent systems which are more evolved and more metal-rich. No difference between z~6 and 8.
FIG 2: offset most striking with respect to z~0 and 2. 

high-redshift star-forming galaxies uniformly having harder ionizing spectra than typical local galaxies at fixed nebular metallicity.

Offset from Sanders 2023 CEERS at z~6 but overlap, maybe because these are more chemically evolved systems (shallower spectra picking brighter galaxies ). Difference between z~7 and z~6 CEERS could suggest that the fraction of more evolved, metal-enriched systems is increasing rapidly from z ∼ 8 to z ∼ 6, despite the bulk of our UV-selected z ∼ 6 sample showing no significant evolution from our z ∼ 8 sample.

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