Candidate high-redshift protoclusters and lensed galaxies in the Planck list of high-z sources overlapping with Herschel-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 of 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 have used archival Herschel-SPIRE observations to study a uniformly-selected sample of 187 PHz sources. In contrast with follow-up studies that were biased towards bright, compact sources, we find that only one of our PHz sources is a bright gravitationally-lensed galaxy (peak flux $\gtrsim 300$ mJy), indicating that such objects are rarer in the PHz catalogue than previously believed ($<1$ per cent). The majority of our PHz sources consist of many red, star-forming galaxies, demonstrating that typical PHz sources are candidate protoclusters. However, our new PHz sources are significantly less bright than found in previous studies and differ in colour, suggesting possible differences in redshift and star-formation rate. Nonetheless, 40 of our PHz sources contain $>3\sigma$ galaxy overdensities, comparable to the fraction of $>3\sigma$ overdensities found in earlier biased studies. We additionally use a machine-learning approach to identify less extreme (peak flux $\sim 100$ mJy) gravitationally-lensed galaxies among Herschel-SPIRE observations of PHz sources, finding a total of seven candidates in our unbiased sample, and 13 amongst previous biased samples. Our new uniformly-selected catalogues of $>3\sigma$ candidate protoclusters and strong gravitational lenses provide interesting targets for follow up with higher-resolution facilities, such as ALMA and JWST.

23 pages, 19 figures, 4 tables. Accepted for publication in MNRAS

References in corpus (16)

• Cosmic Star Formation History
• Popular Ensemble Methods: An Empirical Study
• The Detection of a Population of Submillimeter-Bright, Strongly-Lensed Galaxies
• Astrophysical and Cosmological Information from Large-scale sub-mm Surveys of Extragalactic Sources
• Inference of the Cold Dark Matter substructure mass function at z=0.2 using strong gravitational lenses
• The early phases of galaxy clusters formation in IR: coupling hydrodynamical simulations with GRASIL3D
• Spectroscopic observations of PHz G237.01+42.50: A galaxy protocluster at z=2.16 in the Cosmos field
• Candidate high-z proto-clusters among the Planck compact sources, as revealed by Herschel-SPIRE
• Is there enough star formation in simulated protoclusters?
• On the statistics of proto-cluster candidates detected in the Planck all-sky survey
• SCUBA-2 observations of candidate starbursting protoclusters selected by Planck and Herschel-SPIRE
• Planck's Dusty GEMS. III. A massive lensing galaxy with a bottom-heavy stellar initial mass function at z=1.5
• Planck's Dusty GEMS. II. Extended [CII] emission and absorption in the Garnet at z=3.4 seen with ALMA
• A search for candidate strongly-lensed dusty galaxies in the Planck satellite catalogues
• A new method to search for high redshift clusters using photometric redshifts
• SCUBA-2 overdensities associated with candidate protoclusters selected from Planck data

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• An ALMA spectroscopic survey of the Planck high-redshift object PLCK G073.4-57.5 confirms two protoclusters
• Probing Heavily Obscured AGN in Major Galaxy Mergers Using the mm-X-ray Correlation