The VANDELS survey: a strong correlation between Ly α equivalent width and stellar metallicity at 3 ≤ z ≤ 5. Issue 1 (9th May 2020)

• Record Type: Journal Article
• Authors: Cullen, F; McLure, R J; Dunlop, J S; Carnall, A C; McLeod, D J; Shapley, A E; Amorín, R; Bolzonella, M; Castellano, M; Cimatti, A; Cirasuolo, M; Cucciati, O; Fontana, A; Fontanot, F; Garilli, B; Guaita, L; Jarvis, M J; Pentericci, L; Pozzetti, L; Talia, M; Zamorani, G; Calabrò, A; Cresci, G; Fynbo, J P U; Hathi, N P; Giavalisco, M; Koekemoer, A; Mannucci, F; Saxena, A
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 495:Issue 1(2020)
• Page Start: 1501
• Page End: 1510
• Publication Date: 2020-05-09
• Subjects: galaxies: evolution -- galaxies: high-redshift; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa1260
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present the results of a new study investigating the relationship between observed Ly α equivalent width ( W λ (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 W λ (Ly α) across the range $-58 \, \rm {\mathring{\rm A}} \lesssim$ W λ (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 W λ (Ly α) and Z ⋆ . Our results indicate that Z ⋆ decreases by a factor ≳ 3 between the lowest W λ (Ly α) quartile (〈 W λ (Ly α)$\rangle =-18\, \rm {\mathring{\rm A}}$ ) and the highest W λ (Ly α) quartile (〈 W λ (Ly α)$\rangle =24\, \rm {\mathring{\rm A}}$ ). Similarly, galaxies typically defined as Lyman alpha emitters (LAEs; W λ (Ly α) $\gt 20\, \rm {\mathring{\rm A}}$ ) are, on average, metal poor with respect to the non-LAE galaxy population ( W λ (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 W λ (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.