2014MNRAS.438.2565S

The galaxy cluster CLG0218.3-0510 at z = 1.62 is one of the most distant galaxy clusters known, with a rich multiwavelength data set that confirms a mature galaxy population already in place. Using very deep, wide-area (20Mpcx20Mpc) imaging by Spitzer MIPS at 24µm, in conjunction with Herschel five-band imaging from 100 to 500µm, we investigate the dust-obscured, star formation properties in the cluster and its associated large-scale environment. Our galaxy sample of 693 galaxies at z ∼ 1.62 detected at 24µm (10 spectroscopic and 683 photo-z) includes both cluster galaxies (i.e. within r < 1Mpc projected cluster-centric radius) and field galaxies, defined as the region beyond a radius of 3Mpc. The star formation rates (SFRs) derived from the measured infrared luminosity range from 18 to 2500M_☉/yr, with a median of 55M_☉/yr, over the entire radial range (10Mpc). The cluster's brightest far-infrared galaxy, taken as the centre of the galaxy system, is vigorously forming stars at a rate of 256±70M_☉/yr, and the total cluster SFR enclosed in a circle of 1Mpc is 1161±96M_☉/yr. We estimate a dust extinction of ∼ 3mag by comparing the SFRs derived from [Oii] luminosity with the ones computed from the 24µm fluxes. We find that the in-falling region (1-3Mpc) is special: there is a significant decrement (3.5x) of passive relative to star-forming galaxies in this region, and the total SFR of the galaxies located in this region is lower ( ∼ 130M_☉/yr/Mpc2) than anywhere in the cluster or field, regardless of their stellar mass. In a complementary approach, we compute the local galaxy density, Σ5, and find no trend between SFR and Σ5. However, we measure an excess of star-forming galaxies in the cluster relative to the field by a factor of 1.7, that lends support to a reversal of SF-density relation in CLG0218.