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The Planck satellite has detected cluster candidates via the Sunyaev Zeldovich (SZ) effect, but the optical follow-up required to confirm these candidates is still incomplete, especially at high redshifts and for SZ detections at low significance. In this work we present our analysis of optical observations obtained for 32 Planck cluster candidates using ACAM on the 4.2-m William Herschel Telescope. These cluster candidates were preselected using SDSS, WISE, and Pan-STARRS images to likely represent distant clusters at redshifts $z gtrsim 0.7$. We obtain photometric redshift and richness estimates for all of the cluster candidates from a red-sequence analysis of $r$-, $i$-, and $z$-band imaging data. In addition, long-slit observations allow us to measure the redshifts of a subset of the clusters spectroscopically. The optical richness is often lower than expected from the inferred SZ mass when compared to scaling relations previously calibrated at low redshifts. This likely indicates the impact of Eddington bias and projection effects or noise-induced detections, especially at low SZ-significance. Thus, optical follow-up not only provides redshift measurements, but also an important independent verification method. We find that 18 (7) of the candidates at redshifts $z > 0.5$ ($z > 0.8$) are at least half as rich as expected from scaling relations, thereby clearly confirming these candidates as massive clusters. While the complex selection function of our sample due to our preselection hampers its use for cosmological studies, we do provide a validation of massive high-redshift clusters particularly suitable for further astrophysical investigations.
We present CARMA observations of the three northern unconfirmed galaxy clusters discovered by the PLANCK satellite. We confirm the existence of two massive clusters (PLCKESZ G115.71+17.52 and PLCKESZ G121.11+57.01) at high significance. For these clu
We present SCUBA-2 follow-up of 61 candidate high-redshift Planck sources. Of these, 10 are confirmed strong gravitational lenses and comprise some of the brightest such submm sources on the observed sky, while 51 are candidate proto-cluster fields u
[Abridged] We use the Planck all-sky submm and mm maps to search for rare sources distinguished by extreme brightness, a few hundreds of mJy, and their potential for being situated at high redshift. These cold Planck sources, selected using the High
We characterise the distribution of quasars within dark matter halos using a direct measurement technique for the first time at redshifts as high as $z sim 1$. Using the Planck Sunyaev-Zeldovich (SZ) catalogue for galaxy groups and the Sloan Digital
We present the XMM-Newton follow-up for confirmation of Planck cluster candidates. Twenty-five candidates have been observed to date using snapshot (~10 ksec) exposures, ten as part of a pilot programme to sample a low range of signal-to-noise ratios