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

F. Cullen, R. J. McLure, J. S. Dunlop, S. Khochfar, R. Davé, R. Amorin, M. Bolzonella, A. C. Carnall, 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. MannucciF. Marchi, D. J. McLeod, L. Pentericci, L. Pozzetti, A. E. Shapley, M. Talia, G. Zamorani

Research output: Contribution to journalArticlepeer-review


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 ηMβ with β ≃ −0.4.
Original languageEnglish
Pages (from-to)2038–2060
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Early online date21 May 2019
Publication statusPublished - Aug 2019


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