  Despite significant efforts in the recent years, the physical processes
responsible for the formation of passive galaxies through cosmic time remain
unclear. The shape and evolution of the Stellar Mass Function (SMF) give an
insight into these mechanisms. Taking advantage from the CANDELS and the deep
Hubble Frontier Fields (HFF) programs, we estimated the SMF of total,
star-forming and passive galaxies from z=0.25 to z=2.75 to unprecedented depth,
and focus on the latter population. The density of passive galaxies underwent a
significant evolution over the last 11 Gyr. They account for 60% of the total
mass in the nearby Universe against ~20% observed at z~2.5. The inclusion of
the HFF program allows us to detect, for the first time at z>1.5, the
characteristic upturn in the SMF of passive galaxies at low masses, usually
associated with environmental quenching. We observe two separate populations of
passive galaxies evolving on different timescales: roughly half of the high
mass systems were already quenched at high redshift, while low mass passive
galaxies are gradually building-up over the redshift range probed. In the
framework of environmental-quenching at low masses, we interpret this finding
as evidence of an increasing role of the environment in the build-up of passive
galaxies as a function of time. Finally, we compared our findings with a set of
theoretical predictions. Despite good agreement in some redshift and mass
intervals, none of the models are able to fully reproduce the observations.
This calls for further investigation into the involved physical mechanisms,
both theoretically and observationally, especially with the brand new JWST
data.
