We present a study of the central radio activity of galaxy clusters at high redshift. Using a large sample of galaxy clusters at $0.7<z<1.5$ from the Massive and Distant Clusters of {it WISE} Survey and the Faint Images of the Radio Sky at Twenty-Cen
timeters $1.4$~GHz catalog, we measure the fraction of clusters containing a radio source within the central $500$~kpc, which we term the cluster radio-active fraction, and the fraction of cluster galaxies within the central $500$~kpc exhibiting radio emission. We find tentative ($2.25sigma$) evidence that the cluster radio-active fraction increases with cluster richness, while the fraction of cluster galaxies that are radio-luminous ($L_{1.4~mathrm{GHz}}geq10^{25}$~W~Hz$^{-1}$) does not correlate with richness at a statistically significant level. Compared to that calculated at $0 < z < 0.6$, the cluster radio-active fraction at $0 < z < 1.5$ increases by a factor of $10$. This fraction is also dependent on the radio luminosity. Clusters at higher redshift are much more likely to host a radio source of luminosity $L_{1.4~mathrm{GHz}}gtrsim10^{26}$~W~Hz$^{-1}$ than are lower redshift clusters. We compare the fraction of radio-luminous cluster galaxies to the fraction measured in a field environment. For $0.7<z<1.5$, we find that both the cluster and field radio-luminous galaxy fraction increases with stellar mass, regardless of environment, though at fixed stellar mass, cluster galaxies are roughly $2$ times more likely to be radio-luminous than field galaxies.
We present an analysis of the radial distribution of Active Galactic Nuclei (AGN) in $2300$ galaxy clusters from the Massive and Distant Clusters of {it WISE} Survey (MaDCoWS). MaDCoWS provides the largest coverage of the extragalactic sky for a clus
ter sample at $zsim1$. We use literature catalogs of AGN selected via optical, mid-infrared (MIR), and radio data, and by optical-to-MIR (OIR) color. Stacking the radial distribution of AGN within the $6arcmin$ of the centers of MaDCoWS galaxy clusters, we find a distinct overdensity of AGN within $1arcmin$ of the galaxy cluster center for AGN of all selection methods. The fraction of red galaxies that host AGN as a function of clustercentric distance is, however, dependent on the AGN selection. The fraction of red galaxies in cluster environments that host AGN selected by optical signatures or blue OIR color is at a deficit compared to the field, while MIR-selected and red OIR color AGN are enhanced in the centers of clusters when compared to field levels. The radio-selected AGN fraction is more than $2.5$ times that of the field, implying that the centers of clusters are conducive to the triggering of radio emission in AGN. We do not find a statistically significant change in the AGN fraction as a function of cluster richness. We also investigate the correlation of central radio activity with other AGN in galaxy clusters. Clusters with radio activity have more central AGN than radio-inactive clusters, implying that central cluster radio activity and AGN triggering may be linked.
We present a weak lensing study of the galaxy cluster IDCS J1426.5+3508 at $z=1.75$, which is the highest redshift strong lensing cluster known and the most distant cluster for which a weak lensing analysis has been undertaken. Using F160W, F814W, an
d F606W observations with the Hubble Space Telescope, we detect tangential shear at $2sigma$ significance. Fitting a Navarro-Frenk-White mass profile to the shear with a theoretical median mass-concentration relation, we derive a mass $M_{200,mathrm{crit}}=2.3^{+2.1}_{-1.4}times10^{14}$ M$_{odot}$. This mass is consistent with previous mass estimates from the Sunyaev-Zeldovich (SZ) effect, X-ray, and strong lensing. The cluster lies on the local SZ-weak lensing mass scaling relation observed at low redshift, indicative of minimal evolution in this relation.
