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The SCUBA-2 Cosmology Legacy Survey : the EGS deep field - II. Morphological transformation and multiwavelength properties of faint submillimetre galaxies.

Zavala, J. A. and Aretxaga, I. and Dunlop, J. S. and Michałowski, M. J. and Hughes, D. H. and Bourne, N. and Chapin, E. and Cowley, W. and Farrah, D. and Lacey, C. and Targett, T. and van der Werf, P. (2018) 'The SCUBA-2 Cosmology Legacy Survey : the EGS deep field - II. Morphological transformation and multiwavelength properties of faint submillimetre galaxies.', Monthly notices of the Royal Astronomical Society., 475 (4). pp. 5585-5602.


We present a multiwavelength analysis of galaxies selected at 450 and 850 μm from the deepest SCUBA-2 observations in the Extended Groth Strip (EGS) field, which have an average depth of σ450 = 1.9 and σ850 = 0.46 mJy beam− 1 over ∼70 arcmin2. The final sample comprises 95 sources: 56 (59 per cent) are detected at both wavelengths, 31 (33 per cent) are detected only at 850 μm, and 8 (8 per cent) are detected only at 450 μm. We identify counterparts for 75 per cent of the whole sample. The redshift distributions of the 450 and 850 μm samples peak at different redshifts with median values of z¯=1.66±0.18 and z¯=2.30±0.20 , respectively. However, the two populations have similar IR luminosities, SFRs, and stellar masses, with mean values of 1.5 ± 0.2 × 1012 L⊙, 150 ± 20 M⊙ yr−1, and 9.0 ± 0.6 × 1010 M⊙, respectively. This places most of our sources (≳85 per cent) on the high-mass end of the main sequence of star-forming galaxies. Exploring the IR excess versus UV-slope (IRX-β) relation we find that the most luminous galaxies are consistent with the Meurer law, while the less luminous galaxies lie below this relation. Using the results of a two-dimensional modelling of the HSTH160-band imaging, we derive a median Sérsic index of n=1.4+0.3−0.1 and a median half-light radius of r1/2 = 4.8 ± 0.4 kpc. Based on a visual-like classification in the same band, we find that the dominant component for most of the galaxies at all redshifts is a disc-like structure, although there is a transition from irregular discs to discs with a spheroidal component at z ∼ 1.4, which morphologically supports the scenario of SMGs as progenitors of massive elliptical galaxies.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:23 January 2018
Date deposited:09 April 2018
Date of first online publication:29 January 2018
Date first made open access:09 April 2018

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