The VANDELS survey: a strong correlation between Ly α equivalent width and stellar metallicity at 3 ≤ z ≤ 5

Journal
Date Issued
2020
Author(s)
Cullen, F.
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McLure, R. J.
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Dunlop, J. S.
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Carnall, A. C.
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McLeod, D. J.
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Shapley, A. E.
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Amorín, R.
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•
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Cimatti, A.
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Cirasuolo, M.
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•
•
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Guaita, L.
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Jarvis, M. J.
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•
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Talia, M.
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Zamorani, G.
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Calabrò, A.
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Fynbo, J. P. U.
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Hathi, N. P.
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Giavalisco, M.
•
Koekemoer, A.
•
•
DOI
Abstract
We present the results of a new study investigating the relationship between observed Ly α equivalent width (Wλ(Ly α)) 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(Ly α) across the range $-58 \,\rm {\mathring{\rm A}} \lesssim$ Wλ(Ly α) $\lesssim 110 \,\rm {\mathring{\rm A}}$ , we determine Z⋆ from full spectral fitting of composite far-ultraviolet spectra and find a clear anticorrelation between Wλ(Ly α) and Z⋆. Our results indicate that Z⋆ decreases by a factor ≳ 3 between the lowest Wλ(Ly α) quartile (λ(Ly α) $\rangle =-18\,\rm {\mathring{\rm A}}$ ) and the highest Wλ(Ly α) quartile (λ(Ly α) $\rangle =24\,\rm {\mathring{\rm A}}$ ). Similarly, galaxies typically defined as Lyman alpha emitters (LAEs; Wλ(Ly α) $\gt 20\,\rm {\mathring{\rm A}}$ ) are, on average, metal poor with respect to the non-LAE galaxy population (Wλ(Ly α) $\le 20\,\rm {\mathring{\rm A}}$ ) 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 ${\simeq}15{-}25{{\ \rm per\ cent}}$ of the observed variation in Wλ(Ly α) across our sample, with the remaining contribution ( ${\simeq}75{-}85{{\ \rm per\ cent}}$ ) being due to a decrease in the H I/dust covering fractions in low- Z⋆ galaxies.
Volume
495
Issue
1
Start page
1501
Uri
Url
Issn Identifier
0035-8711
Ads BibCode
2020MNRAS.495.1501C
Rights
open.access
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