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Register a new userThe Massive and Distant Clusters of WISE Survey X: Initial Results from a Sunyaev-Zeldovich Effect Study of Massive Galaxy Clusters at z>1 using MUSTANG2 on the GBT
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The properties of galaxy clusters as a function of redshift can be utilized as an important cosmological tool. We present initial results from a program of follow-up observations of the Sunyaev-Zeldovich effect (SZE) in high redshift galaxy clusters detected at infrared wavelengths in the Massive and Distant Clusters of WISE Survey (MaDCoWS). Using typical on-source integration times of 3-4 hours per cluster, MUSTANG2 on the Green Bank Telescope was able to measure strong detections of SZE decrements and statistically significant masses on 14 out of 16 targets. On the remaining two, weaker (3.7 sigma) detections of the SZE signal and strong upper limits on the masses were obtained. In this paper we present masses and pressure profiles of each target and outline the data analysis used to recover these quantities. Of the clusters with strong detections, three show significantly flatter pressure profiles while, from the MUSTANG2 data, five others show signs of disruption at their cores. However, outside of the cores of the clusters, we were unable to detect significant amounts of asymmetry. Finally, there are indications that the relationship between optical richness used by MaDCoWS and SZE-inferred mass may be significantly flatter than indicated in previous studies.
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We present CARMA 30 GHz Sunyaev-Zeldovich (SZ) observations of five high-redshift ($z gtrsim 1$), infrared-selected galaxy clusters discovered as part of the all-sky Massive and Distant Clusters of WISE Survey (MaDCoWS). The SZ decrements measured toward these clusters demonstrate that the MaDCoWS selection is discovering evolved, massive galaxy clusters with hot intracluster gas. Using the SZ scaling relation calibrated with South Pole Telescope clusters at similar masses and redshifts, we find these MaDCoWS clusters have masses in the range $M_{200} approx 2-6 times 10^{14}$ $M_odot$. Three of these are among the most massive clusters found to date at $zgtrsim 1$, demonstrating that MaDCoWS is sensitive to the most massive clusters to at least $z = 1.3$. The added depth of the AllWISE data release will allow all-sky infrared cluster detection to $z approx 1.5$ and beyond.
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 gas constraints from Sunyaev-Zeldovich (SZ) effect measurements in a sample of eleven X-ray and infrared (IR) selected galaxy clusters at z >=1, using data from the Sunyaev-Zeldovich Array (SZA). The cylindrically integrated Compton-y parameter, Y , is calculated by fitting the data to a two-parameter gas pressure profile. Where possible, we also determine the temperature of the hot intra-cluster plasma from Chandra and XMM-Newton data, and constrain the gas mass within the same aperture (r_2500 ) as Y . The SZ effect is detected in the clusters for which the X-ray data indicate gas masses above ~ 10^13 Msun, including XMMU J2235-2557 at redshift z = 1.39, which to date is one of the most distant clusters detected using the SZ effect. None of the IR-selected targets are detected by the SZA measurements, indicating low gas masses for these objects. For these and the four other undetected clusters, we quote upper limits on Y and Mgas_SZ , with the latter derived from scaling relations calibrated with lower redshift clusters. We compare the constraints on Y and X-ray derived gas mass Mgas_X-ray to self-similar scaling relations between these observables determined from observations of lower redshift clusters, finding consistency given the measurement error.
The Sunyaev-Zeldovich Effect (SZE) has been observed toward six massive galaxy clusters, at redshifts 0.091 leq z leq 0.322 in the 86-102 GHz band with the Y. T. Lee Array for Microwave Background Anisotropy (AMiBA). We modify an iterative method, based on the isothermal beta-models, to derive the electron temperature T_e, total mass M_t, gas mass M_g, and integrated Compton Y within r_2500, from the AMiBA SZE data. Non-isothermal universal temperature profile (UTP) beta models are also considered in this paper. These results are in good agreement with those deduced from other observations. We also investigate the embedded scaling relations, due to the assumptions that have been made in the method we adopted, between these purely SZE-deduced T_e, M_t, M_g and Y. Our results suggest that cluster properties may be measurable with SZE observations alone. However, the assumptions built into the pure-SZE method bias the results of scaling relation estimations and need further study.
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