H-ATLAS: a candidate high redshift cluster/protocluster of star-forming galaxies

• Published in: Monthly notices of the Royal Astronomical Society 2016-09, Vol.461 (2), p.1719-1733
• Main Authors: Clements, D. L., Braglia, F., Petitpas, G., Greenslade, J., Cooray, A., Valiante, E., De Zotti, G., O'Halloran, B., Holdship, J., Morris, B., Pérez-Fournon, I., Herranz, D., Riechers, D., Baes, M., Bremer, M., Bourne, N., Dannerbauer, H., Dariush, A., Dunne, L., Eales, S., Fritz, J., Gonzalez-Nuevo, J., Hopwood, R., Ibar, E., Ivison, R. J., Leeuw, L. L., Maddox, S., Michałowski, M. J., Negrello, M., Omont, A., Oteo, I., Serjeant, S., Valtchanov, I., Vieira, J. D., Wardlow, J., van der Werf, P.
• Format: Article
• Language: English
• Subjects: Arrays; Astrophysics; Color; Colour; Flux; Galactic clusters; Galaxies; Red shift; Sciences of the Universe; Space telescopes; Spectral energy distribution; Star & galaxy formation; Starbursts
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stw1224

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 (S 870 > ∼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.