Astraeus V: the emergence and evolution of metallicity scaling relations during the epoch of reionization

Graziano Ucci, Pratika Dayal, Anne Hutter, Chiaki Kobayashi, Stefan Gottloeber, Gustavo Yepes, Leslie Hunt, Laurent Legrand, Crescenzo Tortora

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In this work, we have implemented a detailed physical model of galaxy chemical enrichment into the ASTRAEUS (seminumerical rAdiative tranSfer coupling of galaxy formaTion and Reionization in N-body dark matter simUlationS) framework which couples galaxy formation and reionization in the first billion years. Simulating galaxies spanning over 2.5 orders of magnitude in halo mass with Mh∼108.9−1011.5M⊙ (⁠Mh∼108.9−1012.8M⊙⁠) at z ∼ 10 (5), we find: (i) smooth accretion of metal-poor gas from the intergalactic medium (IGM) plays a key role in diluting the interstellar medium interstellar medium metallicity which is effectively restored due to self-enrichment from star formation; (ii) a redshift averaged gas-mass loading factor that depends on the stellar mass as ηg≈1.38(M∗/1010M⊙)−0.43⁠; (iii) the mass–metallicity relation is already in place at z ∼ 10 and shows effectively no redshift evolution down to z ∼ 5; (iv) for a given stellar mass, the metallicity decreases with an increase in the star formation rate (SFR); (v) the key properties of the gas-phase metallicity (in units of 12 + log(O/H), stellar mass, SFR and redshift are linked through a high-redshift fundamental plane of metallicity (HFPZ) for which we provide a functional form; (vi) the mass–metallicity–SFR relations are effectively independent of the reionization radiative feedback model for M∗∼>106.5M⊙ galaxies; (vii) while low-mass galaxies (⁠Mh∼<109M⊙⁠) are the key contributors to the metal budget of the IGM at early times, higher mass haloes provide about 50 per cent of the metal budget at lower redshifts.
Original languageEnglish
Pages (from-to)3557–3575
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date30 Nov 2022
Publication statusPublished - 30 Jan 2023


  • astro-ph.GA
  • galaxies: formation
  • galaxies: evolution
  • galaxies: abundances
  • methods: numerical
  • galaxies: high-redshift


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