Background: According to the big bang theory the first galaxies wouldn't have any "metals" (elements other than hydrogen and helium) in them. Metals would have to build up over time in the universe. Alternatively, a nonexpanding universe wouldln't show any correlation between redshift and metallicity.
Disclaimer: This is a hodge-podge of different studies of different types of objects that I've found through googling. I use this page to keep track of the datasets and relevant articles I find, and I add to it when I find more. It's not presented as conclusive evidence for anything in particular. If you know of any z and 12+log(O/H) datasets that I can add, send them to mike@mikehelland.com.
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| Year | Name | z (redshift) | 12+log(O/H) |
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The most reliable metallicity measurements are based on the flux ratio of the [O iii] λ4363 line against [O iii] λ5007. The technique is called the Te method, because it determines the electron temperature (Te) of the gas, and hence the gas-phase oxygen-to-hydrogen (O/H) abundance (Aller 1984; Izotov et al. 2006). However, detecting [O iii] λ4363 is difficult, because it is weak and almost undetectable in metal-rich galaxies. For example, only 0.3% of the strongly star-forming galaxies in the Sloan Digital Sky Survey (SDSS) have 2σ or better detections of [O iii] λ4363 (Izotov et al. 2006; Nagao et al. 2006).
We measured the equivalent widths of the [O ii]λ3727, Hβ, and [O iii]λλ4959,5007 emission lines observed in the galaxy spectra obtained with the Visible Multi-Object Spectrograph mounted at the Very Large Telescope. For each galaxy, we derived the metallicity-sensitive emission-line ratio R23, ionization-sensitive emission-line ratio O32, and gas-phase oxygen abundance 12 + log (O/H).