The MOSDEF survey: Mass, metallicity, and star-formation rate at z ∼ 2.3

Ryan L. Sanders, Alice E. Shapley, Mariska Kriek, Naveen A. Reddy, William R. Freeman, Alison L. Coil, Brian Siana, Bahram Mobasher, Irene Shivaei, Sedona H. Price, Laura De Groot

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197 Scopus citations


We present results on the z ∼ 2.3 mass-metallicity relation (MZR) using early observations from the MOSFIRE Deep Evolution Field survey. We use an initial sample of 87 star-forming galaxies with spectroscopic coverage of Hβ, [OIII] λ5007, Hα, and [NII] λ6584 rest-frame optical emission lines, and estimate the gas-phase oxygen abundance based on the N2 and O3N2 strong-line indicators. We find a positive correlation between stellar mass and metallicity among individual z ∼ 2.3 galaxies using both the N2 and O3N2 indicators. We also measure the emission-line ratios and corresponding oxygen abundances for composite spectra in bins of stellar mass. Among composite spectra, we find a monotonic increase in metallicity with increasing stellar mass, offset ∼0.15-0.3 dex below the local MZR. When the sample is divided at the median star-formation rate (SFR), we do not observe significant SFR dependence of the z ∼ 2.3 MZR among either individual galaxies or composite spectra. We furthermore find that z ∼ 2.3 galaxies have metallicities ∼0.1 dex lower at a given stellar mass and SFR than is observed locally. This offset suggests that high-redshift galaxies do not fall on the local "fundamental metallicity relation" among stellar mass, metallicity, and SFR, and may provide evidence of a phase of galaxy growth in which the gas reservoir is built up due to inflow rates that are higher than star-formation and outflow rates. However, robust conclusions regarding the gas-phase oxygen abundances of high-redshift galaxies await a systematic reappraisal of the application of locally calibrated metallicity indicators at high redshift.

Original languageEnglish
Article number138
JournalAstrophysical Journal
Issue number2
StatePublished - Feb 1 2015

Bibliographical note

Publisher Copyright:
© 2015. The American Astronomical Society. All rights reserved.


  • Galaxies: ISM
  • Galaxies: abundances
  • Galaxies: evolution
  • Galaxies: high-redshift

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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