  The identities of the main processes triggering and quenching star-formation
in galaxies remain unclear. A key stage in evolution, however, appears to be
represented by post-starburst galaxies. To investigate their impact on galaxy
evolution, we initiated a multiwavelength study of galaxies with k+a spectral
features in the COSMOS field. We examine a mass-selected sample of k+a galaxies
at z=0.48-1.2 using the spectroscopic zCOSMOS sample. K+a galaxies occupy the
brightest tail of the luminosity distribution. They are as massive as quiescent
galaxies and populate the green valley in the colour versus luminosity (or
stellar mass) distribution. A small percentage (<8%) of these galaxies have
radio and/or X-ray counterparts (implying an upper limit to the SFR of
~8Msun/yr). Over the entire redshift range explored, the class of k+a galaxies
is morphologically a heterogeneous population with a similar incidence of
bulge-dominated and disky galaxies. This distribution does not vary with the
strength of the Hdelta absorption line but instead with stellar mass in a way
reminiscent of the well-known mass-morphology relation. Although k+a galaxies
are also found in underdense regions, they appear to reside typically in a
similarly rich environment as quiescent galaxies on a physical scale of
~2-8Mpc, and in groups they show a morphological early-to-late type ratio
similar to the quiescent galaxy class. With the current data set, we do not
find evidence of statistical significant evolution in either the number/mass
density of k+a galaxies at intermediate redshift with respect to the local
values, or the spectral properties. Those galaxies, which are affected by a
sudden quenching of their star-formation activity, may increase the stellar
mass of the red-sequence by up to a non-negligible level of ~10%.
