SPIRE and the formation and evolution of galaxy clusters

The progenitors of local galaxy clusters (protoclusters) are powerful laboratories for tracing the emergence of large scale structure and studying the evolution of galaxies in dense environments.We propose to use SPIRE.s excellent sensitivity and survey speed to obtain, for the first time, a large sample of dustobscured, star forming, protocluster galaxies in an area encompassing the entire protocluster and its environment.The 8 protoclusters in the sample cover the key redshift range 2 < z < 4 and have a wealth of existing, multiwavelength data and a large number of spectroscopically confirmed protocluster galaxies. The masses of the protoclusters are typically a few times 10^14 10^15 solar masses and the cores are up to 40 times denser than the field.Matching the SPIRE sources with upcoming LOFAR and EVLA radio observations, we will constrain the photometric redshifts to better than 0.3, resulting in a complete sample of dusty protocluster galaxies with very low (<5%) contamination.The proposed SPIRE observations will be compared to our extensive simulations of forming protoclusters, allowing us to: (i) unveil and characterize the (dustobscured) starforming galaxies in the protoclusters and constrain their star formations rates and dust temperature; (ii) relate these properties to their optical morphologies, stellar masses and location in the protocluster and investigate the differences between protocluster galaxies and field galaxies; (iii) ascertain whether red protocluster galaxies are passive galaxies or dusty starbursts; (iv) determine the structure and size of the protoclusters, in particular, distinguish whether galaxies are distributed homogeneously or in filaments; (v) trace the evolution and contraction of largescale structures from z4 to z2.The protocluster targets are ideally located for followup spectroscopy and highresolution imagin truncated!, Please see [truncated!, Please see actual data for full text]