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Register a new userThe Massive and Distant Clusters of WISE Survey IX: High Radio Activity in a Merging Cluster
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We present a multi-wavelength investigation of the radio galaxy population in the galaxy cluster MOO J1506+5137 at $z$=1.09$pm$0.03, which in previous work we identified as having multiple complex radio sources. The combined dataset used in this work includes data from the Low-Frequency Array Two-metre Sky Survey (LoTSS), NSFs Karl G. Jansky Very Large Array (VLA), the Robert C. Byrd Green Bank Telescope (GBT), the Spitzer Space Telescope, and the Dark Energy Camera Legacy Survey (DECaLS). We find that there are five radio sources which are all located within 500 kpc ($sim$1$^{prime}$) of the cluster center and have radio luminosities $P_{mathrm{1.4GHz}}$ > 1.6$times$10$^{24}$ W Hz$^{-1}$. The typical host galaxies are among the highest stellar mass galaxies in the cluster. The exceptional radio activity among the massive galaxy population appears to be linked to the dynamical state of the cluster. The galaxy distribution suggests an ongoing merger, with a subgroup found to the northwest of the main cluster. Further, two of the five sources are classified as bent-tail sources with one being a potential wide-angle tail (WAT)/hybrid morphology radio source (HyMoRS) indicating a dynamic environment. The cluster also lies in a region of the mass-richness plane occupied by other merging clusters in the Massive and Distant Clusters of WISE Survey (MaDCoWS). The data suggest that during the merger phase radio activity can be dramatically enhanced, which would contribute to the observed trend of increased radio activity in clusters with increasing redshift.
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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-Centimeters $1.4$~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 the results from a study with NSFs Karl G. Jansky Very Large Array (VLA) to determine the radio morphologies of extended radio sources and the properties of their host galaxies in 50 massive galaxy clusters at z~1. We find a majority of the radio morphologies to be Fanaroff-Riley (FR) type IIs. By analyzing the infrared counterparts of the radio sources, we find that ~40% of the host galaxies are the candidate brightest cluster galaxy (BCG) and ~83% are consistent with being one of the top six most massive galaxies in the cluster. We investigate the role of environmental factors on the radio-loud AGN population by examining correlations between environmental and radio-galaxy properties. We find that the highest stellar mass hosts ($M_{*} gtrsim$ 4$times 10^{11} M_{odot}$) are confined to the cluster center and host compact jets. There is evidence for an increase in the size of the jets with cluster-centric radius, which may be attributed to the decreased ICM pressure confinement with increasing radius. Besides this correlation, there are no other significant correlations between the properties of the radio-AGN (luminosity, morphology, or size) and environmental properties (cluster richness and location within the cluster). The fact that there are more AGN in the cluster environment than the field at this epoch, combined with the lack of strong correlation between galaxy and environmental properties, argues that the cluster environment fosters radio activity but does not solely drive the evolution of these sources at this redshift.
We present measurements of the stellar mass fractions ($f_star$) for a sample of high-redshift ($0.93 le z le 1.32$) infrared-selected galaxy clusters from the Massive and Distant Clusters of WISE Survey (MaDCoWS) and compare them to the stellar mass fractions of Sunyaev-Zeldovich (SZ) effect-selected clusters in a similar mass and redshift range from the South Pole Telescope (SPT)-SZ Survey. We do not find a significant difference in mean $f_star$ between the two selection methods, though we do find an unexpectedly large range in $f_star$ for the SZ-selected clusters. In addition, we measure the luminosity function of the MaDCoWS clusters and find $m^*= 19.41pm0.07$, similar to other studies of clusters at or near our redshift range. Finally, we present SZ detections and masses for seven MaDCoWS clusters and new spectroscopic redshifts for five MaDCoWS clusters. One of these new clusters, MOO J1521+0452 at $z=1.31$, is the most distant MaDCoWS cluster confirmed to date.
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 cluster 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.
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