MUFASA: The strength and evolution of galaxy conformity in various tracers
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Date
2017
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Publisher
Oxford University Press
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 low-mass quenched satellite galaxies compared to observations. Mufasa
produces conformity in observed properties such as colour, 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 intro-
duce 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 & 1 Mpc. 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. Metal-
licity shows a curious anti-conformity 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 ~ 1012M⊙. 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.
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Keywords
Galaxies, Evolution, Formation, Statistics, N-body simulations
Citation
Rafieferantsoa, M. & Dave, R. (2017). MUFASA: The strength and evolution of galaxy conformity in various tracers