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Disentangling a group of lensed submm galaxies at z∼ 2.9.

MacKenzie, T.P. and Scott, D. and Smail, I. and Chapin, E.L. and Chapman, S.C. and Conley, A. and Cooray, A. and Dunlop, J.S. and Farrah, D. and Fich, M. and Gibb, A.G. and Holland, W.S. and Ivison, R.J. and Jenness, T. and Kneib, J.-P. and Marsden, G. and Richard, J. and Robson, E.I. and Valtchanov, I. and Wardlow, J.L. (2014) 'Disentangling a group of lensed submm galaxies at z∼ 2.9.', Monthly notices of the Royal Astronomical Society., 445 (1). pp. 201-212.


MS 0451.6−0305 is a rich galaxy cluster whose strong lensing is particularly prominent at submm wavelengths. We combine new Submillimetre Common-User Bolometer Array (SCUBA)-2 data with imaging from Herschel Spectral and Photometric Imaging Receiver (SPIRE) and PACS and Hubble Space Telescope in order to try to understand the nature of the sources being lensed. In the region of the ‘giant submm arc’, we uncover seven multiply imaged galaxies (up from the previously known four), of which six are found to be at a redshift of z ∼ 2.9, and possibly constitute an interacting system. Using a novel forward-modelling approach, we are able to simultaneously deblend and fit spectral energy distributions to the individual galaxies that contribute to the giant submm arc, constraining their dust temperatures, far-infrared luminosities, and star formation rates (SFRs). The submm arc first identified by SCUBA can now be seen to be composed of at least five distinct sources, four of these within a galaxy group at z ∼ 2.9. Only a handful of lensed galaxy groups at this redshift are expected on the sky, and thus this is a unique opportunity for studying such systems in detail. The total unlensed luminosity for this galaxy group is (3.1 ± 0.3) × 1012 L⊙, which gives an unlensed SFR of (450 ± 50) M⊙ yr−1. This finding suggests that submm source multiplicity, due to physically associated groupings as opposed to chance alignment, extends to fainter flux densities than previously discovered. Many of these systems may also host optical companions undetected in the submm, as is the case here.

Item Type:Article
Keywords:Gravitational lensing: strong, Methods: data analysis, Galaxies: clusters: individual, Galaxies: interactions, Galaxies: starburst, Submillimetre: galaxies.
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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2014 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:No date available
Date deposited:24 November 2014
Date of first online publication:November 2014
Date first made open access:No date available

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