Publication Date:
2014-02-15
Description:
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 (20 Mpc 20 Mpc) imaging by Spitzer MIPS at 24 μm, in conjunction with Herschel five-band imaging from 100 to 500 μm, 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 24 μm (10 spectroscopic and 683 photo- z ) includes both cluster galaxies (i.e. within r 〈 1 Mpc projected cluster-centric radius) and field galaxies, defined as the region beyond a radius of 3 Mpc. The star formation rates (SFRs) derived from the measured infrared luminosity range from 18 to 2500 M yr –1 , with a median of 55 M yr –1 , over the entire radial range (10 Mpc). The cluster's brightest far-infrared galaxy, taken as the centre of the galaxy system, is vigorously forming stars at a rate of 256 ± 70 M yr –1 , and the total cluster SFR enclosed in a circle of 1 Mpc is 1161 ± 96 M yr –1 . We estimate a dust extinction of ~3 mag by comparing the SFRs derived from [O ii ] luminosity with the ones computed from the 24 μm fluxes. We find that the in-falling region (1–3 Mpc) is special: there is a significant decrement (3.5 x ) of passive relative to star-forming galaxies in this region, and the total SFR of the galaxies located in this region is lower (~130 M yr –1 Mpc –2 ) than anywhere in the cluster or field, regardless of their stellar mass. In a complementary approach, we compute the local galaxy density, 5 , and find no trend between SFR and 5 . 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.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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