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The VANDELS survey: the stellar metallicities of star-forming galaxies at 2.5 <z <5.0

Research output: Contribution to journalArticle

  • R. Amorin
  • M. Bolzonella
  • M. Castellano
  • A. Cimatti
  • M. Cirasuolo
  • G. Cresci
  • J. P. U. Fynbo
  • F. Fontanot
  • A. Gargiulo
  • B. Garilli
  • L. Guaita
  • N. Hathi
  • P. Hibon
  • F. Mannucci
  • F. Marchi
  • D. J. McLeod
  • L. Pentericci
  • L. Pozzetti
  • A. E. Shapley
  • M. Talia
  • G. Zamorani

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Original languageEnglish
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Early online date21 May 2019
Publication statusPublished - 1 Aug 2019


We present the results of a study utilizing ultradeep, rest-frame UV, spectroscopy to quantify the relationship between stellar mass and stellar metallicity for 681 star-forming galaxies at 2.5 < z < 5.0 (〈z〉 = 3.5 ± 0.6) drawn from the VANDELS survey. Via a comparison with high-resolution stellar population synthesis models, we determine stellar metallicities (Z∗, here a proxy for the iron abundance) for a set of high signal-to-noise ratio composite spectra formed from subsamples selected by mass and redshift. Across the stellar mass range 8.5<log(⟨M∗⟩/M⊙)<10.2⁠, we find a strong correlation between stellar metallicity (Z∗/Z⊙) and stellar mass, with stellar metallicity monotonically increasing from Z∗/Z⊙ < 0.09 at ⟨M∗⟩=3.2×108M⊙ to Z∗/Z⊙ = 0.27 at ⟨M∗⟩=1.7×1010M⊙⁠. In contrast, at a given stellar mass, we find no evidence for significant metallicity evolution across the redshift range of our sample. However, comparing our results to the z = 0 stellar mass–metallicity relation for star-forming galaxies, we find that the 〈z〉 = 3.5 relation is consistent with being shifted to lower metallicities by ≃0.6 dex at all stellar masses. Contrasting our derived stellar metallicities with estimates of the gas-phase metallicities of galaxies at similar redshifts and stellar masses, we find evidence for enhanced O/Fe ratios in z ≳ 2.5 star-forming galaxies of the order (O/Fe) ≳ 1.8 × (O/Fe)⊙. Finally, by comparing our results to the predictions of three cosmological simulations, we find that the 〈z〉 = 3.5 stellar mass–metallicity relation is consistent with current predictions for how outflow strength scales with galaxy stellar mass. This conclusion is supported by an analysis of one-zone analytic chemical evolution models, and suggests that the mass-loading parameter (⁠η=M˙outflow/M∗⁠) scales as η∝Mβ∗ with β ≃ −0.4.

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  • astro-ph.GA

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