By determining the nature of all the Planck compact sources within 808.4 deg2 of large Herschel
surveys, we have identified 27 candidate protoclusters of dusty
star-forming galaxies (DSFGs) that are at least 3σ overdense in either
250, 350, or 500 μm sources. We find roughly half of all the Planck compact sources are resolved by Herschel into multiple discrete objects, with the other half remaining unresolved by Herschel. We find a significant difference between versions of the Planck
catalogues, with earlier releases hosting a larger fraction of
candidate protoclusters and Galactic cirrus than later releases, which
we ascribe to a difference in the filters used in the creation of the
three catalogues. We find a surface density of DSFG candidate
protoclusters of (3.3 ± 0.7) × 10−2 sources deg−2, in good agreement with previous similar studies. We find that a Planck colour selection of S857/S545 < 2 works well to select candidate protoclusters, but can miss protoclusters at z < 2. The Herschel colours of individual candidate protocluster members indicate our candidate protoclusters all likely all lie at z > 1.
Our candidate protoclusters are a factor of 5 times brighter at 353 GHz
than expected from simulations, even in the most conservative
estimates. Further observations are needed to confirm whether these
candidate protoclusters are physical clusters, multiple protoclusters
along the line of sight, or chance alignments of unassociated sources.
Resubmitted to MNRAS after request for minor revision