Candidate high-redshift protoclusters and lensed galaxies in the <i>Planck</i> list of high-<i>z</i> sources overlapping with <i>Herschel</i>-SPIRE imaging

ABSTRACT The Planck list of high-redshift source candidates (the PHz catalogue) contains 2151 peaks in the cosmic infrared background, unresolved by Planck’s 5 arcmin beam. Follow-up spectroscopic observations have revealed that some these objects are $z\, {\approx }\, 2$ protoclusters and strong gravitational lenses but an unbiased survey has not yet been carried out. To this end, we used archival Herschel-SPIRE to study a uniformly selected sample 187 sources. In contrast with follow-up studies were biased towards bright, compact sources, find only one our sources is bright gravitationally lensed galaxy (peak flux ${\gtrsim 300$ mJy), indicating such rarer catalogue than previously believed (&amp;lt;1 per cent). majority consist many red, star-forming galaxies, demonstrating typical candidate protoclusters. However, new significantly less found previous differ colour, suggesting possible differences redshift star formation rate. None less, 40 contain ${\gt 3\, \sigma$ overdensities, comparable fraction overdensities earlier studies. We additionally use machine-learning approach identify extreme ${\sim 100$ mJy) galaxies among finding total seven sample, 13 amongst samples. Our catalogues provide interesting targets for follow up higher resolution facilities, as ALMA JWST.