LoCuSS: pre-processing in galaxy groups falling into massive galaxy clusters at z = 0.2

We report direct evidence of pre-processing of the galaxies residing in galaxy groups falling into galaxy clusters drawn from the Local Cluster Substructure Survey (LoCuSS). 34 groups have been identified via theirX-ray emission in the infall regions of 23 massive ( = 10(15) M-circle dot) clusters at 0.15 < z < 0.3. Highly complete spectroscopic coverage combined with 24 mu m imaging from Spitzer allows us to make a consistent and robust selection of cluster and group members including star-forming galaxies down to a stellar mass limit of M* = 2 x 10(10) M-circle dot. The fraction f(SF) of star-forming galaxies in infalling groups is lower and with a flatter trend with respect to clustercentric radius when compared to the rest of the cluster galaxy population. At R approximate to 1.3 r(200), the fraction of star-forming galaxies in infalling groups is half that in the cluster galaxy population. This is direct evidence that star-formation quenching is effective in galaxies already prior to them settling in the cluster potential, and that groups are favourable locations for this process.Science and Technology Facilities Council [ST/N000633/1]; PRIN INAFThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu