A submillimetre-bright z~3 overdensity behind a z~1 supercluster revealed by SCUBA-2 and Herschel

Abstract

We present a wide-field (30' diameter) 850um SCUBA-2 map of the spectacular three-component merging supercluster, RCS 231953+00, at z=0.9. The brightest submillimetre galaxy (SMG) in the field (S_850=12mJy) is within 30" of one of the cluster cores (RCS 2319-C), and is likely to be a more distant, lensed galaxy. Interestingly, the wider field around RCS 2319-C reveals a local overdensity of SMGs, exceeding the average source density by a factor of 4.5, with a <1 per cent chance of being found in a random field. Utilizing Herschel-SPIRE observations, we find three of these SMGs have similar submillimetre colours. We fit their observed 250-850um spectral energy distributions to estimate their redshift, yielding 2.5<z<3.5, and calculate prodigious star formation rates (SFRs) ranging from 500-2500 solar masses per year. We speculate that these galaxies are either lensed SMGs, or signpost a physical structure at z~3: a 'protocluster' inhabited by young galaxies in a rapid phase of growth, destined to form the core of a massive galaxy cluster by z=0.

6 pages, 4 colour figures; accepted for publication in MNRAS Letters

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Cited by in corpus (7)

• An excess of dusty starbursts related to the Spiderweb galaxy
• HerMES: Clusters of Dusty Galaxies Uncovered by Herschel and Planck
• Planck intermediate results. XXVII. High-redshift infrared galaxy overdensity candidates and lensed sources discovered by Planck and confirmed by Herschel-SPIRE
• Candidate high-z proto-clusters among the Planck compact sources, as revealed by Herschel-SPIRE
• Cluster candidates around low power radio-galaxies at z~1-2 in COSMOS
• H-ATLAS: A Candidate High Redshift Cluster/Protocluster of Star-Forming Galaxies
• MAGIC: Muse gAlaxy Groups In Cosmos -- A survey to probe the impact of environment on galaxy evolution over the last 8 Gyr