Abstract
An analysis of more than 3000 galaxies resolved at better than 114pc/h at
z=0.62 in a LAOZI cosmological adaptive mesh refinement hydrodynamic simulation
is performed and insights gained on quenching and color migration. The vast
majority of red galaxies are found to be within three virial radii of a larger
galaxy, at the onset of quenching. We shall thus call this mechanism
``environment quenching", which encompasses satellite quenching. Two physical
processes are largely responsible: ram-pressure stripping first disconnects the
galaxy from the cold gas supply on large scales, followed by a longer period of
cold gas starvation taking place in high velocity dispersion environment,
during the early part of which the existing dense cold gas in the central
region (=<10kpc) is consumed by in situ star formation. Quenching is found to
be more efficient but not faster, on average, in denser environment. Throughout
quenching galaxies follow nearly vertical tracks in the color-stellar-mass
diagram. In contrast, individual galaxies of all masses grow most of their
stellar masses in the blue cloud, prior to the onset of quenching, and
progressively more massive blue galaxies with already relatively older mean
stellar ages continue to enter the red sequence. Consequently, correlations
among observables of red galaxies - such as the age-mass relation - are largely
inherited from their blue progenitors at the onset of quenching. While the
color makeup of the entire galaxy population strongly depends on environment,
which is a direct result of environment quenching, physical properties of blue
galaxies as a sub-population show little dependence on environment. A variety
of predictions from the simulation are shown to be in accord with extant
observations.
Description
[1311.5916] How Galaxies Become Red: Insights from Cosmological Simulations
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