The SAMI Galaxy Survey: Using concentrated star formation and stellar population ages to understand environmental quenching

We study environmental quenching using the spatial distribution of current star-formation and stellar population ages with full SAMI Galaxy Survey. By a concentration index [C-index, defined as log10(r_{50,Halpha}/r_{50,cont})], we separate our sample into regular galaxies (C-index>-0.2) centrally concentrated (SF-concentrated; C-index<-0.2). Concentrated is potential indicator currently undergoing `outside-in' quenching. Our environments cover ungrouped galaxies, low-mass groups (M_200<10^12.5 M_sun), high-mass (M_200 in range 10^{12.5-14} M_sun) clusters (M_200>10^14 M_sun). find fraction SF-concentrated increases halo mass 9\pm2 per cent, 8\pm3 19\pm4 cent 29\pm4 for groups, clusters, respectively. interpret these results evidence clusters. To investigate time-scale calculate light-weighted age (Age_L) mass-weighted (Age_M) spectral fitting, well Dn4000 Hdelta_A indices. assume that average galaxy radial profile before entering group or cluster similar to galaxies. At large radius (1-2 R_e), have older than an difference 1.83\pm0.38 Gyr Age_L 1.34\pm0.56 Age_M. This suggests while can be effective process will not quickly quench entire galaxy. In contrast, at 1-2 R_e are consistent (0.19\pm0.21 Age_L, 0.40\pm0.61 Age_M), suggesting must rapid.