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, specific star formation rate (sSFR),
and H I 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 ≳ 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 H
I 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 ˜1012
M⊙. 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 language | English |
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Pages (from-to) | 955-973 |
Journal | Monthly Notices of the Royal Astronomical Society |
Volume | 475 |
Issue number | 1 |
DOIs | |
Publication status | Published - 21 Dec 2017 |
Keywords / Materials (for Non-textual outputs)
- methods: numerical
- galaxies: evolution
- galaxies: formation
- galaxies: statistics