Herschel unveils the nature of high-z openPar2<z<4closePar protocluster candidates selected by Planck

The Planck mission has the unique capability of finding systematically and on the whole sky the rarest, most luminous high redshift submm sources. These can be lensed objects or protogroups/clusters of galaxies containing many individual sources forming stars at very high rates. Our full sample of candidates contains about 1 source per 30 sq. deg., and already 3 candidates have been confirmed as interesting highz sources: one was found to be a protogroup at zvirgul3, based on a SPIRE OT1 pilot project; and 2 others are zvirgul34.6 sources already found in the HATLAS and around A773. We now propose to use SPIRE to image a larger set of Planck sources to obtain a statistically significant sample of 70 highz protogroups and clusters. This will give new insights into the early evolution of galaxies in the highest density regions, improving our understanding of the relationship between the growth of structures and starformation, and placing constraints on the level of nonGaussianity within the LCDM model. This program exploits the exceptional synergy and complementarity between Planck and Herschel. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]