The reversal of the SF-density relation in a massive, X-ray-selected galaxy cluster at z = 1.58: Results from Herschel

Dusty, star-forming galaxies have a critical role in the formation and evolution of massive galaxies in the Universe. Using deep far-infrared imaging in the range 100-500 μm obtained with the Herschel telescope, we investigate the dust-obscured star formation (SF) in the galaxy cluster XDCP J0044.0-2033 at z = 1.58, the most massive cluster at z > 1.5, with a measured mass M200 = 4.7^{+1.4}_{-0.9} × 1014 M⊙. We perform an analysis of the spectral energy distributions (SEDs) of 12 cluster members (5 spectroscopically confirmed) detected with ≥3σ significance in the PACS maps, all ultraluminous infrared galaxies. The individual star formation rates (SFRs) lie in the range 155-824 M⊙ yr-1, with dust temperatures of 24-35 K. We measure a strikingly high amount of SF in the cluster core, SFR (<250 kpc) ≥ 1875 ± 158 M⊙ yr-1, four times higher than the amount of SF in the cluster outskirts. This scenario is unprecedented in a galaxy cluster, showing for the first time a reversal of the SF-density relation at z ˜ 1.6 in a massive cluster.