MUFASA: The strength and evolution of galaxy conformity in various tracers

Mika Rafieferantsoa, Romeel Davé

Research output: Contribution to journalArticle

5 Scopus citations

Abstract

We investigate galaxy conformity using the MUFASA cosmological hydrodynamical simulation. We show a bimodal distribution in galaxy colour with radius, albeit with too many lowmass quenched satellite galaxies compared to observations. MUFASA produces conformity in observed properties such as colour, specific star formation rate (sSFR), and HI content, i.e. neighbouring galaxies have similar properties. We see analogous trends in other properties such as in environment, stellar age, H2 content, and metallicity. We introduce quantifying conformity using S(R), measuring the relative difference in upper and lower quartile properties of the neighbours. We show that low-mass and non-quenched haloes have weak conformity (S(R) ≲ 0.5) extending to large projected radii R in all properties, while high-mass and quenched haloes have strong conformity (S(R) ~ 1) that diminishes rapidly with R and disappears at R ≳ 1Mpc. S(R) is strongest for environment in low-mass haloes, and sSFR (or colour) in high-mass haloes, and is dominated by one-halo conformity with the exception of HI in small haloes. Metallicity shows a curious anticonformity in massive haloes. Tracking the evolution of conformity for z = 0 galaxies back in time shows that conformity broadly emerges as a late-time (z ≲ 1) phenomenon. However, for fixed halo mass bins, conformity is fairly constant with redshift out to z ≳ 2. These trends are consistent with the idea that strong conformity only emerges once haloes grow above MUFASA's quenching mass scale of ~1012Mo˙. A quantitative measure of conformity in various properties, along with its evolution, thus represents a new and stringent test of the impact of quenching on environment within current galaxy formation models.

Original languageEnglish (US)
Article numberstx3293
Pages (from-to)955-973
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Volume475
Issue number1
DOIs
StatePublished - Mar 21 2018

Keywords

  • Galaxies: Evolution
  • Galaxies: Formation
  • Galaxies: Statistics
  • Methods: Numerical

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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