A recalibration of strong-line oxygen abundance diagnostics via the direct method and implications for the high-redshift universe
Abstract
We use direct method oxygen abundances in combination with strong optical emission lines, stellar masses (M⋆), and star formation rates (SFRs) to recalibrate the N2, O3N2, and N2O2 oxygen abundance diagnostics. We stack spectra of ∼200 000 star-forming galaxies from the Sloan Digital Sky Survey in bins of M⋆ and SFR offset from the star-forming main sequence ( {Δ log (SSFR)}) to measure the weak emission lines needed to apply the direct method. All three new calibrations are reliable to within ±0.10 dex from log (M⋆/M⊙) ∼ 7.5-10.5 and up to at least 200 M⊙ yr-1 in SFR. The N2O2 diagnostic is the least subject to systematic biases. We apply the diagnostics to galaxies in the local Universe and investigate the M⋆-Z-SFR relation. The N2 and O3N2 diagnostics suggest the SFR dependence of the M⋆-Z-SFR relation varies with both M⋆ and {Δ log (SSFR)}, whereas the N2O2 diagnostic suggests a nearly constant dependence on SFR. We apply our calibrations to a sample of high-redshift galaxies from the literature, and find them to be metal-poor relative to local galaxies with similar M⋆ and SFR. The calibrations do reproduce direct method abundances of the local analogues. We conclude that the M⋆-Z-SFR relation evolves with redshift.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 2016
- DOI:
- 10.1093/mnras/stw392
- arXiv:
- arXiv:1602.01087
- Bibcode:
- 2016MNRAS.458.1529B
- Keywords:
-
- ISM: abundances;
- galaxies: abundances;
- galaxies: active;
- galaxies: evolution;
- galaxies: ISM;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 21 pages, 14 figures. Resubmitted to MNRAS. For a brief video explaining this paper, see https://www.youtube.com/watch?v=OpoeguZi2X4