Dissecting the nature of the Planck-HFI high-z blobs

Ultra luminous dusty galaxies radiating most of their energy in the far IR are now known from Spitzer IR and submillimeter observations to dominate the integrated luminosity at redshift 2 to 3. The behavior of this population at higher redshifts remains poorly constrained. This proposal is based on the use of the Planck all sky survey at millimeter and submillimeter wavelengths to find new and rare highz candidate sources. The limited angular resolution requires a specific data processing to extract good candidates. The Cosmic Infrared Background (CIB) is observed with high signal to noise by Planck after a specific component separation. An algorithm detecting cold spots on the CIB (thus potentially high z dominated) compatible with point sources has been developed. These high z blobs have been shown to be a mixture of different type of objects. Among these, new high z ULIRGS at the high end of the luminosity function or lensed, or high z large scale structures are very interesting for galaxy evolution. We performed comparison of the Planck data with new unidentified sources found by SPT near the upper end of their luminosity function and we detected a few of them. Furthermore, the stacking in Planck of 34 of these SPT sources is easily detected in Planck and gives a typical SED in the Planck bands for these sources. We thus selected sources with this type of SED in the Planck data and produced a list of 10 candidates proposed in this program for observations with SPIRE and PACS. We propose an observation allowing to study the nature of these 10 cold blobs in three cases covering well the possible contributors to this Planck detected high z blobs (single source, cluster of 10 to 20 sources, structure of the cold CIB spot if a small number of sources has not been found).This should be a very interesting contribution to the study of this new emerging population. Furthermore this program should allow us to use best t [truncated!, Please see actual data for full text]