The Massive and Distant Clusters of WISE Survey 2: A Stacking Analysis Investigating the Evolution of Star Formation Rates and Stellar Masses in Groups and Clusters

The evolution of galaxies depends on their masses and local environments;understanding when and how environmental quenching starts to operate remains achallenge. Furthermore, studies of the high-redshift regime have been limitedto massive cluster members, owing to sensitivity limits or small fields ofviews when the sensitivity is sufficient, intrinsically biasing the picture ofcluster evolution. In this work, we use stacking to investigate the averagestar formation history of more than 10,000 groups and clusters drawn from theMassive and Distant Clusters of WISE Survey 2 (MaDCoWS2). Our analysis coversnear ultraviolet to far infrared wavelengths, for galaxy overdensities at 0.5≲ z ≲ 2.54. We employ SED fitting to measure the specific starformation rates (sSFR) in four annular apertures with radii between 0 and 1000kpc. At z ≳ 1.6, the average sSFR evolves similarly to the field inboth the core and the cluster outskirts. Between z = 1.60 andz = 1.35, the sSFR in the core drops sharply, and continues tofall relative to the field sSFR at lower redshifts. We interpret this change asevidence that the impact of environmental quenching dramatically increases atz ∼ 1.5, with the short time span of the transition suggesting that theenvironmental quenching mechanism dominant at this redshift operates on a rapidtimescale. We find indications that the sSFR may decrease with increasing hosthalo mass, but lower-scatter mass tracers than the signal-to-noise ratio (S/N)are needed to confirm this relationship.