The VANDELS survey: A strong correlation between Lyα equivalent width and stellar metallicity at 3≤z≤5

F. Cullen, R. J. McLure, J. S. Dunlop, A. C. Carnall, D. J. McLeod, A. E. Shapley, R. Amorín, M. Bolzonella, M. Castellano, A. Cimatti, M. Cirasuolo, O. Cucciati, A. Fontana, F. Fontanot, B. Garilli, L. Guaita, M. J. Jarvis, L. Pentericci, L. Pozzetti, M. TaliaG. Zamorani, A. Calabrò, G. Cresci, J. P. U. Fynbo, N. P. Hathi, M. Giavalisco, A. Koekemoer, F. Mannucci, A. Saxena

Research output: Contribution to journalArticlepeer-review


We present the results of a new study investigating the relationship between observed Lyα equivalent width (Wλ(Lyα)) and the metallicity of the ionizing stellar population (Z⋆) for a sample of 768 star-forming galaxies at 3≤z≤5 drawn from the VANDELS survey. Dividing our sample into quartiles of rest-frame Wλ(Lyα) across the range −58Å≲ Wλ(Lyα) ≲110Å we determine Z⋆ from full spectral fitting of composite far-ultraviolet (FUV) spectra and find a clear anti-correlation between Wλ(Lyα) and Z⋆. Our results indicate that Z⋆ decreases by a factor ≳3 between the lowest Wλ(Lyα) quartile (⟨Wλ(Lyα)⟩=−18Å) and the highest Wλ(Lyα) quartile (⟨Wλ(Lyα)⟩=24Å). Similarly, galaxies typically defined as Lyman Alpha Emitters (LAEs; Wλ(Lyα) >20Å) are, on average, metal poor with respect to the non-LAE galaxy population (Wλ(Lyα) ≤20Å) with Z⋆non−LAE≳2× Z⋆LAE. Finally, based on the best-fitting stellar models, we estimate that the increasing strength of the stellar ionizing spectrum towards lower Z⋆ is responsible for ≃15−25% of the observed variation in Wλ(Lyα) across our sample, with the remaining contribution (≃75−85%) being due to a decrease in the HI/dust covering fractions in low Z⋆ galaxies.
Original languageEnglish
Pages (from-to)1501-1510
Number of pages11
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date9 May 2020
Publication statusPublished - 1 Jun 2020


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