| Description |
We propose to obtain PACS/SPIRE imaging observations of XMM0044 at redshift z=1.58, one of the most massive, distant X-ray 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 star-formation activity in the cluster galaxy population, at a critical epoch for cluster assembly. Based on its X-ray luminosity we estimate the cluster mass range to be 3.5-5x10^14 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 follow-up observations unveiled a population of disturbed galaxies, with on-going star-formation 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 star-formation rates of the cluster population in XMM0044 at z=1.6, by integrating the galaxies far-infrared (FIR) luminosity provided by PACS+SPIRE photometry. The observational window opened by Herschel straddles the critical peak of FIR emission of z=1-2 galaxies, providing a direct measurement of the on-going star-formation 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 star-formation properties of distant galaxy clusters that up to now has been out of reach, in order to provide a comprehensive understanding of SF activityin high-density environments and the study of the evolution of the morphology-density relation.The requested observations will be the deepest FIR data of a high-z cluster, allowing us to reach star-formation rates as low as 50 Msun/yr (corresponding to Luminous Infrared Galaxies), a limit that is currently out of reach for zvirgul1 clusters. |
