Deciphering stellar metallicities in the early Universe: case study of a young galaxy at z = 4.77 in the MUSE eXtremely Deep Field - INSU - Institut national des sciences de l'Univers Access content directly
Journal Articles Astronomy and Astrophysics - A&A Year : 2022

Deciphering stellar metallicities in the early Universe: case study of a young galaxy at z = 4.77 in the MUSE eXtremely Deep Field

Jorryt Matthee
  • Function : Author
Anna Feltre
  • Function : Author
Michael Maseda
  • Function : Author
Themiya Nanayakkara
  • Function : Author
Leindert Boogaard
  • Function : Author
Anne Verhamme
  • Function : Author
Floriane Leclercq
  • Function : Author
Haruka Kusakabe
  • Function : Author
Tanya Urrutia
  • Function : Author
Lutz Wisotzki
  • Function : Author

Abstract

Directly characterising the first generations of stars in distant galaxies is a key quest of observational cosmology. We present a case study of ID53 at z = 4.77, the UV-brightest (but L) star-forming galaxy at z > 3 in the MUSE eXtremely Deep Field with a mass of ≈109 M. In addition to very strong Lyman-α (Lyα) emission, we clearly detect the (stellar) continuum and an N V P Cygni feature, interstellar absorption, fine-structure emission and nebular C IV emission lines in the 140 h spectrum. Continuum emission from two spatially resolved components in Hubble Space Telescope data are blended in the MUSE data, but we show that the nebular C IV emission originates from a subcomponent of the galaxy. The UV spectrum can be fit with recent BPASS stellar population models combined with single-burst or continuous star formation histories (SFHs), a standard initial mass function, and an attenuation law. Models with a young age and low metallicity (log10(age/yr) = 6.5-7.6 and [Z/H] = −2.15 to −1.15) are preferred, but the details depend on the assumed SFH. The intrinsic Hα luminosity of the best-fit models is an order of magnitude higher than the Hα luminosity inferred from Spitzer/IRAC data, which either suggests a high escape fraction of ionising photons, a high relative attenuation of nebular to stellar dust, or a complex SFH. The metallicity appears lower than the metallicity in more massive galaxies at z = 3 − 5, consistent with the scenario according to which younger galaxies have lower metallicities. This chemical immaturity likely facilitates Lyα escape, explaining why the Lyα equivalent width is anti-correlated with stellar metallicity. Finally, we stress that uncertainties in SFHs impose a challenge for future inferences of the stellar metallicity of young galaxies. This highlights the need for joint (spatially resolved) analyses of stellar spectra and photo-ionisation models.

Based on observations obtained with the Very Large Telescope under the large program 1101.A-0127.

Fichier principal
Vignette du fichier
aa42187-21.pdf (1.62 Mo) Télécharger le fichier
Origin Publisher files allowed on an open archive

Dates and versions

insu-03711525 , version 1 (02-07-2022)

Identifiers

Cite

Jorryt Matthee, Anna Feltre, Michael Maseda, Themiya Nanayakkara, Leindert Boogaard, et al.. Deciphering stellar metallicities in the early Universe: case study of a young galaxy at z = 4.77 in the MUSE eXtremely Deep Field. Astronomy and Astrophysics - A&A, 2022, 660, ⟨10.1051/0004-6361/202142187⟩. ⟨insu-03711525⟩
9 View
24 Download

Altmetric

Share

Gmail Mastodon Facebook X LinkedIn More