3.1. k+a galaxies at low redshift

The occurrence of k+a galaxies at low z is believed to be low, both in the field (0.1%, [58]) and in clusters [59]. In Coma and other nearby clusters, Balmer strong galaxies have been reported at a "reduced frequency and burst strength" (= weaker Balmer lines) compared to distant clusters ([14, 15, 60] and references therein). It has been suggested that in Coma this Balmer strong galaxies are preferentially associated with the NGC4839 group infalling from South-West [14], and the central concentration of the latest star formation activity seems to support the post-starburst scenario [60]. Recently, in a magnitude-limited new spectroscopic survey of Coma galaxies, we find no k+a galaxy as luminous as those in distant clusters, but a significant population of faint k+a's (dwarf galaxies, M_V > - 18.5), with no preference for the NGC4839 group [61]. This work suggests that, while strong-lined k+a spectra in luminous galaxies appear to be an important phenomenon in distant clusters, in the local Universe the k+a incidence is mostly related with dwarf galaxies.