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

Matthee JJ, Feltre A, Maseda M, Nanayakkara T, Boogaard L, Bacon R, Verhamme A, Leclercq F, Kusakabe H, Urrutia T, Wisotzki L. 2022. Deciphering stellar metallicities in the early universe: Case study of a young galaxy at z = 4.77 in the MUSE eXtremely Deep Field. Astronomy & Astrophysics. 660, A10.

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Matthee, Jorryt JISTA ; Feltre, Anna; Maseda, Michael; Nanayakkara, Themiya; Boogaard, Leindert; Bacon, Roland; Verhamme, Anne; Leclercq, Floriane; Kusakabe, Haruka; Urrutia, Tanya; Wisotzki, Lutz
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.
Publishing Year
Date Published
2022-03-30
Journal Title
Astronomy & Astrophysics
Acknowledgement
We thank the referee for thoughtful and constructive comments that have improved the quality of this manuscript. Based on observations collected at the European Southern Observatory under ESO programme 1101.A-0127. This work made use of v2.2.1 of the Binary Population and Spectral Synthesis (BPASS) models as described in Eldridge et al. (2017) and Stanway & Eldridge (2018). A.F. acknowledges the support from grant PRIN MIUR2017-20173ML3WW_001. T.N. acknowledges support from Australian Research Council Laureate Fellowship FL180100060.
Volume
660
Article Number
A10
ISSN
eISSN
IST-REx-ID

Cite this

Matthee JJ, Feltre A, Maseda M, 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 & Astrophysics. 2022;660. doi:10.1051/0004-6361/202142187
Matthee, J. J., Feltre, A., Maseda, M., Nanayakkara, T., Boogaard, L., Bacon, R., … Wisotzki, L. (2022). Deciphering stellar metallicities in the early universe: Case study of a young galaxy at z = 4.77 in the MUSE eXtremely Deep Field. Astronomy & Astrophysics. EDP Sciences. https://doi.org/10.1051/0004-6361/202142187
Matthee, Jorryt J, Anna Feltre, Michael Maseda, Themiya Nanayakkara, Leindert Boogaard, Roland Bacon, Anne Verhamme, 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 & Astrophysics. EDP Sciences, 2022. https://doi.org/10.1051/0004-6361/202142187.
J. J. Matthee 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 & Astrophysics, vol. 660. EDP Sciences, 2022.
Matthee JJ, Feltre A, Maseda M, Nanayakkara T, Boogaard L, Bacon R, Verhamme A, Leclercq F, Kusakabe H, Urrutia T, Wisotzki L. 2022. Deciphering stellar metallicities in the early universe: Case study of a young galaxy at z = 4.77 in the MUSE eXtremely Deep Field. Astronomy & Astrophysics. 660, A10.
Matthee, Jorryt J., 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 & Astrophysics, vol. 660, A10, EDP Sciences, 2022, doi:10.1051/0004-6361/202142187.
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