  Galaxy quenching is a critical step in galaxy evolution. In this work, we
present a statistical study of galaxy quenching in 17 cluster candidates at
0.5<z<1.0 in the COSMOS field. We selected cluster members with a wide range of
stellar mass and environment to study their mass and environment dependence.
Member galaxies are classified into star-forming, quiescent and
recently-quenched galaxies (RQG) using the rest-frame UVJ diagram. We further
separated fast and slow quenching RQGs by model evolutionary tracks on the UVJ
diagram. We defined the quenching efficiency as the ratio of RQGs over
star-forming galaxies and the quenching stage as the ratio of RQGs over
quiescent galaxies to quantify the quenching processes. We found quenching
efficiency is enhanced by both higher stellar mass and denser environment.
Massive or dense environment galaxies quench earlier. Slow quenching is more
dominant for massive galaxies and at lower redshifts, but no clear dependence
on the environment is found. Our results suggest that low-mass galaxies in
dense environments are likely quenched through a short-timescale process such
as ram pressure stripping, while massive galaxies in a sparse environment are
mostly quenched by a longer-timescale process. Using the line strength of
H$\delta$ and [OII], we confirmed that our UVJ method to select RQGs agrees
with high S/N DEIMOS spectra. However, we caution that the visibility time
(duration of a galaxy's stay in the RQG region on the UVJ diagram) may also
depend on mass or environment. The method introduced in this work can be
applied to RQG candidates for future statistical RQG spectroscopic surveys. The
systematic spectroscopic RQG study will disentangle the degeneracy between
visibility time and quenching properties.
