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Title: The mass-metallicity and fundamental metallicity relations at z > 2 using very large telescope and Subaru near-infrared spectroscopy of zCOSMOS galaxies

In the local universe, there is good evidence that, at a given stellar mass M, the gas-phase metallicity Z is anti-correlated with the star formation rate (SFR) of the galaxies. It has also been claimed that the resulting Z(M, SFR) relation is invariant with redshift—the so-called 'fundamental metallicity relation' (FMR). Given a number of difficulties in determining metallicities, especially at higher redshifts, the form of the Z(M, SFR) relation and whether it is really independent of redshift is still very controversial. To explore this issue at z > 2, we used VLT-SINFONI and Subaru-MOIRCS near-infrared spectroscopy of 20 zCOSMOS-deep galaxies at 2.1 < z < 2.5 to measure the strengths of up to five emission lines: [O II] λ3727, Hβ, [O III] λ5007, Hα, and [N II] λ6584. This near-infrared spectroscopy enables us to derive O/H metallicities, and also SFRs from extinction corrected Hα measurements. We find that the mass-metallicity relation (MZR) of these star-forming galaxies at z ≈ 2.3 is lower than the local Sloan Digital Sky Survey (SDSS) MZR by a factor of three to five, a larger change than found by Erb et al. using [N II]/Hα-based metallicities from stacked spectra. We discuss how the different selectionsmore » of the samples and metallicity calibrations used may be responsible for this discrepancy. The galaxies show direct evidence that the SFR is still a second parameter in the MZR at these redshifts. However, determining whether the Z(M, SFR) relation is invariant with epoch depends on the choice of extrapolation used from local samples, because z > 2 galaxies of a given mass have much higher SFRs than the local SDSS galaxies. We find that the zCOSMOS galaxies are consistent with a non-evolving FMR if we use the physically motivated formulation of the Z(M, SFR) relation from Lilly et al., but not if we use the empirical formulation of Mannucci et al.« less
Authors:
;  [1] ; ;  [2] ;  [3] ;  [4] ;  [5]
  1. Department of Astrophysics, University of Vienna, Türkenschanzstrasse 17, A-1180 Vienna (Austria)
  2. Institute of Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland)
  3. Institut de Recherche en Astrophysique et Planétologie, CNRS, 14 avenue Édouard Belin, F-31400 Toulouse (France)
  4. Instituto de Astrofísica de Andalucia, CSIC, Apartado de Correos 3004, E-18080 Granada (Spain)
  5. Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, Giessenbachstrasse, D-85741 Garching b. München (Germany)
Publication Date:
OSTI Identifier:
22365256
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 792; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION SPECTROSCOPY; CALIBRATION; ELEMENT ABUNDANCE; EMISSION; EVOLUTION; EXTRAPOLATION; FERROMAGNETIC RESONANCE; GALAXIES; INFRARED SPECTRA; MASS; METALLICITY; RED SHIFT; STARS; TELESCOPES; UNIVERSE