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摘要
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-1 content, i.e. neighbouring galaxies have similar properties. We see analogous trends in other properties such as in environment, stellar age, H-2 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) less than or similar to 0.5) extending to large projected radii R in all properties, while high-mass and quenched haloes have strong conformity (S(R) similar to 1) that diminishes rapidly with R and disappears at R greater than or similar to 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 (1) 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 less than or similar to 1) phenomenon. However, for fixed halo mass bins, conformity is fairly constant with redshift out to z greater than or similar to 2. These trends are consistent with the idea that strong conformity only emerges once haloes grow above MUFASA'S quenching mass scale of similar to 10(12) M-circle dot. 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.
- 出版日期2018-3
