Tracing star-formation at the dawn of cluster assembly in the galaxy cluster XMM0044 at z=1.6

We propose to obtain PACS/SPIRE imaging observations of XMM0044 at redshift z1.58, one of the most massive, distant Xray luminous cluster known to date, which was discovered within the XMM Distant Cluster Project. With the proposed data we will obtain an unbiased characterization of starformation activity in the cluster galaxy population, at a critical epoch for cluster assembly. Based on its Xray luminosity we estimate the cluster mass range to be 3.55x10^14 Msun, indicating that this cluster already has a massive halo, at a cosmic epoch when cluster galaxies are observed to undergo significant structural and color transformation. Our optical NIR/IR followup observations unveiled a population of disturbed galaxies, with ongoing starformation and compelling evidence of merger activity in the brightest galaxies. The compact core with 4 galaxies within a radius of 3 is suggestive of the early formation stage of a BCG.The goal of this 10.2 hr program is to measure accurate starformation rates of the cluster population in XMM0044 at z1.6, by integrating the galaxies farinfrared (FIR) luminosity provided by PACS+SPIRE photometry. The observational window opened by Herschel straddles the critical peak of FIR emission of z12 galaxies, providing a direct measurement of the ongoing starformation activity derived from the total infrared luminosity a technique that is unaffected by the uncertainties associated to extrapolations to the IR. Herschel is therefore fundamental to provide a view of the starformation properties of distant galaxy clusters that up to now has been out of reach, in order to provide a comprehensive understanding of SF activityin highdensity environments and the study of the evolution of the morphologydensity relation.The requested observations will be the deepest FIR data of a highz cluster, allowing us to reach starformation rates as low as 50 Msun/yr (corresponding to Luminous Infrar truncated!, Please [truncated!, Please see actual data for full text]