Detection of a CMB decrement towards a cluster of mJy radiosources

Abstract

We present the results of radio, optical and near-infrared observations of the field of TOC J0233.3+3021, a cluster of milliJansky radiosources from the TexOx Cluster survey. In an observation of this field with the Ryle Telescope (RT) at 15 GHz, we measure a decrement in the cosmic microwave background (CMB) of $-675\pm 95\mu$Jy on the RT's $\approx$ 0.65 k$\lambda$ baseline. Using optical and infrared imaging with the McDonald 2.7-m Smith Reflector, Calar Alto 3.5-m telescope and UKIRT, we identify the host galaxies of five of the radiosources and measure magnitudes of $R\approx 24$, $J\approx 20$, $K\approx 18$. The CMB decrement is consistent with the Sunyaev-Zel'dovich (SZ) effect of a massive cluster of galaxies, which if modelled as a spherical King profile of core radius ${\theta }_C=20^{\prime \prime }$ has a central temperature decrement of $900\mu$K. The magnitudes and colours of the galaxies are consistent with those of old ellipticals at $z\sim 1$. We therefore conclude that TOC J0233.3+3021 is a massive, high redshift cluster. These observations add to the growing evidence for a significant population of massive clusters at high redshift, and demonstrate the effectiveness of combining searches for AGN `signposts' to clusters with the redshift-independence of the SZ effect.

Six pages; accepted for publication in MNRAS. Version with full-resolution UV plot available from http://www.mrao.cam.ac.uk/~garret/MB185.ps

References in corpus (5)

• Galaxy Cluster Gas Mass Fractions from Sunyaev-Zel'dovich Effect Measurements: Constraints on Omega_M
• Surveying the Sky with the Arcminute MicroKelvin Imager: Expected Constraints on Galaxy Cluster Evolution and Cosmology
• Sunyaev-Zel'dovich Effect Imaging of Massive Clusters of Galaxies at Redshift z > 0.8
• Chandra detection of the intracluster medium around 3C294 at z=1.786
• Mapping of the SZ effect in the cluster Cl 0016+16 with the Ryle Telescope

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• Spectroscopic follow-up of a cluster candidate at z = 1.45
• Searching for Clusters with SUMSS
• High-redshift clusters from NVSS: The TexOx Cluster (TOC) Survey