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The SCUBA-2 Cosmology Legacy Survey : ALMA resolves the rest-frame far-infrared emission of sub-millimeter galaxies.

Simpson, J. M. and Smail, I. and Swinbank, A. M. and Almaini, O. and Blain, A. W. and Bremer, M. N. and Chapman, S. C. and Chen, C.-C. and Conselice, C. and Coppin, K. E. K. and Danielson, A. L. R. and Dunlop, J. S. and Edge, A. C. and Farrah, D. and Geach, J. E. and Hartley, W. G. and Ivison, R. J. and Karim, A. and Lani, C. and Ma, C.-J. and Meijerink, R. and Michalowski, M. J. and Mortlock, A. and Scott., D. and Simpson, C.J. and Spanns, M. and Thomson, A. P. and van Kampen, E. and van der Werf, P. P. (2015) 'The SCUBA-2 Cosmology Legacy Survey : ALMA resolves the rest-frame far-infrared emission of sub-millimeter galaxies.', Astrophysical journal., 799 (1). p. 81.

Abstract

We present high-resolution (0.''3) Atacama Large Millimeter Array 870 μm imaging of 52 sub-millimeter galaxies (SMGs) in the Ultra Deep Survey field to investigate the size and morphology of the sub-millimeter (sub-mm) emission on 2-10 kpc scales. We derive a median intrinsic angular size of FWHM = 0.''30 ± 0.''04 for the 23 SMGs in the sample detected at a signal-to-noise ratio (S/N) >10. Using the photometric redshifts of the SMGs we show that this corresponds to a median physical half-light diameter of 2.4 ± 0.2 kpc. A stacking analysis of the SMGs detected at S/N <10 shows they have sizes consistent with the 870 μm bright SMGs in the sample. We compare our results to the sizes of SMGs derived from other multi-wavelength studies, and show that the rest-frame ~250 μm sizes of SMGs are consistent with studies of resolved 12CO (J = 3-2 to 7-6) emission lines, but that sizes derived from 1.4 GHz imaging appear to be approximately two times larger on average, which we attribute to cosmic ray diffusion. The rest-frame optical sizes of SMGs are around four times larger than the sub-millimeter sizes, indicating that the star formation in these galaxies is compact relative to the pre-existing stellar distribution. The size of the starburst region in SMGs is consistent with the majority of the star formation occurring in a central region, a few kiloparsecs in extent, with a median star formation rate surface density of 90 ± 30 M ☉ yr–1 kpc–2, which may suggest that we are witnessing an intense period of bulge growth in these galaxies.

Item Type:Article
Keywords:Galaxies: high-redshift, Galaxies: starburst.
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Status:Peer-reviewed
Publisher Web site:http://dx.doi.org/10.1088/0004-637X/799/1/81
Publisher statement:© 2015. The American Astronomical Society. All rights reserved.
Date accepted:15 November 2014
Date deposited:13 April 2015
Date of first online publication:16 January 2015
Date first made open access:No date available

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