Evidence for strong evolution in galaxy environmental quenching efficiency between z = 1.6 and z = 0.9
Abstract
We analyse the evolution of environmental quenching efficiency, the fraction of quenched cluster galaxies that would be star-forming if they were in the field, as a function of redshift in 14 spectroscopically confirmed galaxy clusters with 0.87 < z < 1.63 from the Spitzer Adaptation of the Red-Sequence Cluster Survey (SpARCS). The clusters are the richest in the survey at each redshift. Passive fractions rise from 42-13+10\% at z ~ 1.6 to 80-9+12\% at z ~ 1.3 and 88-3+4\% at z < 1.1, outpacing the change in passive fraction in the field. Environmental quenching efficiency rises dramatically from 16-19+15 at z ~ 1.6 to 62-15+21\% at z ~ 1.3 and 73-7+8\% at z $ 1.1. This work is the first to show direct observational evidence for a rapid increase in the strength of environmental quenching in galaxy clusters at z ~ 1.5, where simulations show cluster-mass halos undergo non-linear collapse and virialisation.