H-ATLAS: a candidate high redshift cluster/protocluster of star-forming galaxies
Pérez-Fournon, I.; Valtchanov, I.; Ivison, R. J.; Omont, A.; Clements, D. L.; Herranz, D.; Bremer, M.; Fritz, J.; Cooray, A.; Ibar, E.; Negrello, M.; De Zotti, G.; Baes, M.; Dannerbauer, H.; Dariush, A.; Dunne, L.; Eales, S.; Hopwood, R.; Maddox, S.; Michałowski, M. J.; Serjeant, S.; Valiante, E.; van der Werf, P.; O'Halloran, B.; Vieira, J. D.; Riechers, D.; Petitpas, G.; Oteo, I.; Bourne, N.; Gonzalez-Nuevo, J.; Greenslade, J.; Wardlow, J.; Braglia, F.; Leeuw, L. L.; Holdship, J.; Morris, B.
United Kingdom, United States, Italy, Spain, Belgium, Austria, New Zealand, Mexico, Chile, Germany, South Africa, France, Denmark, Netherlands
Abstract
We investigate the region around the Planck-detected z = 3.26 gravitationally lensed galaxy HATLAS J114637.9-001132 (hereinafter HATLAS12-00) using both archival Herschel data from the H-ATLAS survey and using submm data obtained with both LABOCA and SCUBA2. The lensed source is found to be surrounded by a strong overdensity of both Herschel-SPIRE sources and submm sources. We detect 17 bright (S870 > ∼7 mJy) sources at >4σ closer than 5 arcmin to the lensed object at 850/870 μm. 10 of these sources have good cross-identifications with objects detected by Herschel-SPIRE which have redder colours than other sources in the field, with 350 μm flux >250 μm flux, suggesting that they lie at high redshift. Submillimeter Array (SMA) observations localise one of these companions to ∼1 arcsec, allowing unambiguous cross identification with a 3.6 and 4.5 μm Spitzer source. The optical/near-IR spectral energy distribution of this source is measured by further observations and found to be consistent with z > 2, but incompatible with lower redshifts. We conclude that this system may be a galaxy cluster/protocluster or larger scale structure that contains a number of galaxies undergoing starbursts at the same time.