Weinzirl, TimAragon-Salamanca, AGray, M EBamford, Steven P.del Pino, Bruno RodríguezChies-Santos, Ana LBohm, AWolf, ChristianCool, Richard2023-06-222023-06-220035-8711http://hdl.handle.net/1885/293664We conduct a comprehensive projected phase-space analysis of the A901/2 multicluster system at z ~ 0.165. Aggregating redshifts from spectroscopy, tunable-filter imaging and prism techniques, we assemble a sample of 856 cluster galaxies reaching 108.5M⊙ in stellar mass. We look for variations in cluster galaxy properties between virialized and non-virialized regions of projected phase space (PPS). Our main conclusions point to relatively gentle environmental effects, expressedmainly on galaxy gas reservoirs. (1) Stacking the four subclusters in A901/2, we find galaxies in the virialized region are more massive, redder and have marginally higher Sérsic indices, but their half-light radii and Hubble types are not significantly different. (2) After accounting for trends in stellar mass, there is a remaining change in rest-frame colour across PPS. Primarily, the colour difference is due to the absence in the virialized region of galaxies with rest frame B - V < 0.7 and moderate-to-high (M(star operator) > 109.85 M⊙) stellar mass. (3) There is an infalling population of lower mass (M(star operator) ≤ 109.85 M⊙), relatively blue (B - V < 0.7) elliptical or spheroidal galaxies that are strikingly absent in the virialized region. (4) The number of bona fide star-forming and active galactic nucleus galaxies in the PPS regions is strongly dictated by stellar mass. However, there remains a reduced fraction of star-forming galaxies in the centres of the clusters at fixed stellar mass, consistent with the star formation-density relation in galaxy clusters. (5) There is no change in specific Hα-derived star formation rates of star-forming galaxies at fixed mass across the cluster environment. This suggests that pre-processing of galaxies during infall plays a prominent role in quenching star formation.This study is based on observations made with the Gran Telescopio Canarias, installed in the Observatorio del Roque de los Muchachos of the Instituto de Astrof´ısica de Canarias, in the island of La Palma. The GTC reference for this programme is GTC2002-12ESO. Access to GTC was obtained through ESO Large Programme 188.A2002. This study is partly based on observations from the European Southern Observatory Very Large Telescope (ESO-VLT), observing run ID 384.A-0813. BRdP acknowledges financial support from the Spanish Ministry of Economy and Competitiveness through grant ESP2015-68964. CW was supported by Australian Research Council Laureate Grant FL0992131.application/pdfen-AU© 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Societyinstrumentation: interferometersgalaxies: clusters: individual: A901/2galaxies: distances and redshiftsgalaxies: star formation201710.1093/MNRAS/STX15252022-04-03