EDGE: The mass-metallicity relation as a critical test of galaxy formation physics

Oscar Agertz, Andrew Pontzen, Justin I. Read, Martin P. Rey, Matthew Orkney, Joakim Rosdahl, Romain Teyssier, Robbert verbeke, Michael Kretschmer, Sarah Nickerson

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

We introduce the 'Engineering Dwarfs at Galaxy Formation's Edge' (EDGE) project to study the cosmological formation and evolution of the smallest galaxies in the Universe. In this first paper, we explore the effects of resolution and sub-grid physics on a single low-mass halo (Mhalo = 109M), simulated to redshift z = 0 at amass and spatial resolution of ∼ 20 M and ∼3 pc. We consider different star formation prescriptions, supernova feedback strengths, and on-the-fly radiative transfer (RT). We show that RT changes the mode of galactic self-regulation at this halo mass, suppressing star formation by causing the interstellar and circumgalactic gas to remain predominantly warm (∼104K) even before cosmic reionization. By contrast, without RT, star formation regulation occurs only through starbursts and their associated vigorous galactic outflows. In spite of this difference, the entire simulation suite (with the exception of models without any feedback) matches observed dwarf galaxy sizes, velocity dispersions, V-band magnitudes, and dynamical mass-to-light-ratios. This is because such structural scaling relations are predominantly set by the host dark matter halo, with the remaining model-to-model variation being smaller than the observational scatter. We find that only the stellar mass-metallicity relation differentiates the galaxy formation models. Explosive feedback ejects more metals from the dwarf, leading to a lower metallicity at a fixed stellar mass. We conclude that the stellar mass-metallicity relation of the very smallest galaxies provides a unique constraint on galaxy formation physics.

Original languageEnglish (US)
Pages (from-to)1656-1672
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Volume491
Issue number2
DOIs
StatePublished - Jan 1 2020
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Galaxies: dwarf
  • Galaxies: evolution
  • Galaxies: formation
  • Galaxies: kinematics and dynamics
  • Local Group
  • Methods: numerical

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