Galaxy environment in the 3D-HST fields. Witnessing the onset of
  satellite quenching at z ~ 1-2
  We make publicly available a catalog of calibrated environmental measures for
galaxies in the five 3D-HST/CANDELS deep fields. Leveraging the spectroscopic
and grism redshifts from the 3D-HST survey, multi wavelength photometry from
CANDELS, and wider field public data for edge corrections, we derive densities
in fixed apertures to characterize the environment of galaxies brighter than
$JH_{140} < 24$ mag in the redshift range $0.5<z<3.0$. By linking observed
galaxies to a mock sample, selected to reproduce the 3D-HST sample selection
and redshift accuracy, each 3D-HST galaxy is assigned a probability density
function of the host halo mass, and a probability that is a central or a
satellite galaxy. The same procedure is applied to a $z=0$ sample selected from
SDSS. We compute the fraction of passive central and satellite galaxies as a
function of stellar and halo mass, and redshift, and then derive the fraction
of galaxies that were quenched by environment specific processes. Using the
mock sample, we estimate that the timescale for satellite quenching is $t_{\rm
quench} \sim 2-5$ Gyr; longer at lower stellar mass or lower redshift, but
remarkably independent of halo mass. This indicates that, in the range of
environments commonly found within the 3D-HST sample, satellites are quenched
by exhaustion of their gas reservoir in absence of cosmological accretion. We
find that the quenching times can be separated into a delay phase during which
satellite galaxies behave similarly to centrals at fixed stellar mass, and a
phase where the star formation rate drops rapidly ($\sim 0.4-0.6$ Gyr), as
shown previously at $z=0$. We conclude that this scenario requires satellite
galaxies to retain a large reservoir of multi-phase gas upon accretion, even at
high redshift, and that this gas sustains star formation for the long quenching
times observed.
