Evidence for galaxies being pre-processed before accreted into clusters

I use the spectroscopic data for galaxies in and around 28 nearby (0.02 <= z <= 0.06) X-ray bright galaxy clusters, to show that the incidence of k+A (or post-starburst) galaxies (EW(H alpha) < 2 angstrom in emission and EW(H delta) > 3 angstrom in absorption) may be correlated with the accretion of small galaxy groups in clusters. At r < 2(r200), the k+A galaxies are found in regions of higher galaxy density relative to other cluster galaxies. The k+A galaxies have a positively skewed distribution of absolute velocity, |v(los)|/sigma(upsilon), where v(los) is the difference between the line-of-sight velocity of the galaxy and the cluster's mean, and sigma(upsilon) is the cluster's velocity dispersion. This distribution is statistically different from that of other cluster galaxies within 2r200, and in the same absolute velocity range. Moreover, 87 per cent of clusters in the sample studied here show statistically significant substructure in their velocity distribution, and 91.4 per cent of all the k+A galaxies are found to be a part of one of these substructures with 4-10 members. These results suggest that star formation in these k+A galaxies is likely to have been quenched due to 'pre-processing' in a poor group-like environment before they are accreted into clusters. I also find a mild, but statistically significant trend in the fraction of k+A galaxies increasing with the temperature of the X-ray emitting gas in clusters.