We use the final data from the VIPERS redshift survey to extract an unparalleled sample of more than 2000 massive \cal { M } \geq 10 ^ { 11 } M _ { \odot } passive galaxies ( MPGs ) at redshift 0.5 \leq z \leq 1.0 , based on their NUV rK colours .
This enables us to investigate how the population of these objects was built up over cosmic time .
We find that the evolution of the number density depends on the galaxy mean surface stellar mass density , \Sigma .
In particular , dense ( \Sigma \geq 2000 M _ { \odot } pc ^ { -2 } ) MPGs show a constant comoving number density over this redshift range , whilst this increases by a factor \sim 4 for the least dense objects , defined as having \Sigma < 1000 M _ { \odot } pc ^ { -2 } .
We estimate stellar ages for the MPG population both fitting the Spectral Energy Distribution ( SED ) and through the D4000 _ { n } index , obtaining results in good agreement .
Our findings are consistent with passive ageing of the stellar content of dense MPGs .
We show that at any redshift the less dense MPGs are younger than dense ones and that their stellar populations evolve at a slower rate than predicted by passive evolution .
This points to a scenario in which the overall population of MPGs was built up over the cosmic time by continuous addition of less dense galaxies : on top of an initial population of dense objects that passively evolves , new , larger , and younger MPGs continuously join the population at later epochs .
Finally , we demonstrate that the observed increase in the number density of MPGs is totally accounted for by the observed decrease in the number density of correspondingly massive star forming galaxies ( i.e .
all the non-passive \cal { M } \geq 10 ^ { 11 } M _ { \odot } objects ) .
Such systems observed at z \simeq 1 in VIPERS , therefore , represent the most plausible progenitors of the subsequent emerging class of larger MPGs .