CARMA observations of massive Planck-discovered cluster candidates at z ≳ 0.5 associated with WISE overdensities: strategy, observations and validation

Abstract

We present 1–2 arcmin spatial resolution Combined Array for Research in Millimetre-wave Astronomy (CARMA)-8 31 GHz observations towards 19 unconfirmed Planck cluster candidates, selected to have significant galaxy overdensities from the WISE early data release and thought to be at z ≳ 1 from the WISE colours of the putative brightest cluster galaxy. We find a Sunyaev–Zeldovich (SZ) detection in the CARMA-8 data towards nine candidate clusters, where one detection is considered tentative. For each cluster candidate we present CARMA-8 maps, a study of their radio-source environment and we assess the reliability of the SZ detection. The CARMA SZ detections appear to be SZ bright, with the mean, primary-beam-corrected peak flux density of the decrement being −2.9 mJy beam^(−1) with a standard deviation of 0.8, and are typically offset from the Planck position by ≈80 arcsec. Using archival imaging data in the vicinity of the CARMA SZ centroids, we present evidence that one cluster matches Abell 586 – a known z ≈ 0.2 cluster; four candidate clusters are likely to have 0.3 ≲ z ≲ 0.7; and, for the remaining four, the redshift information is inconclusive. We also argue that the sensitivity limits resulting from the cross-correlation between Planck and WISE makes it challenging to use our selection criterion to identify clusters at z > 1.

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