MEGATRON: how the first stars can create an iron metallicity plateau in the smallest dwarf galaxies
Abstract
We study the stellar mass-iron metallicity relation of dwarf galaxies in the new high-resolution MEGATRON cosmological radiation-hydrodynamics simulations. These simulations model galaxy formation up to z ≈ 8 in a region that will collapse into a Milky-Way-like galaxy at z = 0 , while self-consistently tracking Population III and II (Pop.~III, Pop.~II) star formation, feedback and chemical enrichment. MEGATRON dwarf galaxies are in excellent agreement with the observed stellar mass-metallicity relation at z = 0 , including an over-abundance of dwarfs along a flat plateau in metallicity () at low stellar masses (). We tie this feature to the chemical enrichment of dwarf galaxies by Pop. III pair-instability supernova (PISN) explosions. The strong Lyman-Werner background (LW) from the protogalaxy ensures that PISNe occur in haloes massive enough () to retain their ejecta. We also predict a tail of ≈ 20 % of iron-deficient () dwarf galaxies. We show that both plateau and tail (i) are robust to large variations in Pop.~II feedback assumptions, and (ii) survive in bound satellites surrounding the central galaxy at z = 0 .
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Authors: Martin P. Rey, Harley Katz, Corentin Cadiou, Mahsa Sanati, Oscar Agertz, Jérémy Blaizot, Alex J. Cameron, Nicholas Choustikov, Julien Devriendt, Uliana Hauk, Alexander P. Ji, Gareth C. Jones, Taysun Kimm, Isaac Laseter, Sergio Martin-Alvarez, Kosei Matsumoto, Yves Revaz, Francisco Rodríguez Montero, Aayush Saxena, Adrianne D. Slyz, Richard Stiskalek, Anatole Storck, Oscar Veenema, Wonjae Yee
Institutions: University of Aberdeen, University of Oxford, Yonsei University, Skåne University Hospital, University of Cambridge, Lund University, University of Wisconsin–Madison, École Polytechnique Fédérale de Lausanne, École Normale Supérieure - PSL, Institut d'Astrophysique de Paris, Centre de Recherche Astrophysique de Lyon