We present photometric measurements for the galaxies – and when possible their bulges and disks – in the 0.05 < z < 0.0585 groups of the Zurich Environmental Study ( ZENS ) ; these measurements include ( B - I ) colors , color gradients and maps , color dispersions , as well as stellar masses and star-formation rates .
The ZENS galaxies are classified into quenched , moderately star-forming , and strongly star-forming using a combination of spectral features and FUV-to-optical colors ; this approach optimally distinguishes quenched systems from dust-reddened star-forming galaxies .
The latter contribute up to 50 \% to the ( B - I ) “ red sequence ” at \sim 10 ^ { 10 } \mbox { $M _ { \odot } $ } .
At fixed morphological or spectral type , we find that galaxy stellar masses are largely independent of environment , and especially of halo mass .
As a first utilization of our photometric database , we study , at fixed stellar mass and Hubble type , how ( B - I ) colors , color gradients and color dispersion of disk satellites depend on group mass M _ { \mathrm { GROUP } } , group-centric distance R / R _ { 200 } and large-scale structure overdensity \delta _ { \mathrm { LSS } } .
The strongest environmental trend is found for disk-dominated satellites with M _ { \mathrm { GROUP } } and R / R _ { 200 } .
At M \lesssim 10 ^ { 10 } M _ { \odot } , disk-dominated satellites are redder in the inner regions of the groups than in the outer parts .
At M \gtrsim 10 ^ { 10 } M _ { \odot } , these satellites have shallower color gradients in higher mass groups and in the cores of groups compared with lower mass groups and the outskirts of groups .
Stellar population analyses and semi-analytic models suggest that disk-dominated satellites undergo quenching of star formation in their outer disks , on timescales \tau _ { \mathrm { quench } } \sim 2 Gyr , as they progressively move inside the group potential .