The Astrophysical Journal (Jan 2024)

The SAGA Survey. V. Modeling Satellite Systems around Milky Way–Mass Galaxies with Updated UniverseMachine

  • Yunchong Wang,
  • Ethan O. Nadler,
  • Yao-Yuan Mao,
  • Risa H. Wechsler,
  • Tom Abel,
  • Peter Behroozi,
  • Marla Geha,
  • Yasmeen Asali,
  • Mithi A. C. de los Reyes,
  • Erin Kado-Fong,
  • Nitya Kallivayalil,
  • Erik J. Tollerud,
  • Benjamin Weiner,
  • John F. Wu

DOI
https://doi.org/10.3847/1538-4357/ad7f4c
Journal volume & issue
Vol. 976, no. 1
p. 119

Abstract

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Environment plays a critical role in shaping the assembly of low-mass galaxies. Here, we use the U niverse M achine (UM) galaxy–halo connection framework and Data Release 3 of the Satellites Around Galactic Analogs (SAGA) Survey to place dwarf galaxy star formation and quenching into a cosmological context. UM is a data-driven forward model that flexibly parameterizes galaxy star formation rates (SFRs) using only halo mass and assembly history. We add a new quenching model to UM, tailored for galaxies with m _⋆ ≲ 10 ^9 M _⊙ , and constrain the model down to m _⋆ ≳ 10 ^7 M _⊙ using new SAGA observations of 101 satellite systems around Milky Way (MW)–mass hosts and a sample of isolated field galaxies in a similar mass range from the Sloan Digital Sky Survey. The new best-fit model, “UM-SAGA,” reproduces the satellite stellar mass functions, average SFRs, and quenched fractions in SAGA satellites while keeping isolated dwarfs mostly star-forming. The enhanced quenching in satellites relative to isolated field galaxies leads the model to maximally rely on halo assembly to explain the observed environmental quenching. Extrapolating the model down to m _⋆ ∼ 10 ^6.5 M _⊙ yields a quenched fraction of ≳30% for isolated field galaxies and ≳80% for satellites of MW-mass hosts at this stellar mass. Spectroscopic surveys can soon test this specific prediction to reveal the relative importance of internal feedback, cessation of mass and gas accretion, satellite-specific gas processes, and reionization for the evolution of faint low-mass galaxies.

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