The SCUBA-2 cosmology legacy survey: ALMA resolves the rest-frame far-infrared emission of sub-millemeter galaxies

Simpson, J.M., Smail, Ian, Swinbank, A.M., Almaini, O., Blain, A.W., Bremer, M.N., Chapman, S.C., Chen, Chian-Chou, Conselice, Christopher J., Coppin, K.E.K., Danielson, A.L.R., Dunlop, J.S., Edge, A.C., Farrah, D., Geach, J.E., Hartley, W.G., Ivison, R.J., Karim, A., Lani, C., Ma, C.-J., Meijerink, R., Michałowski, M.J., Mortlock, A., Scott, D., Simpson, C.J., Spaans, M., Thomson, A.P., 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-millemeter galaxies. Astrophysical Journal, 799 (1). p. 81. ISSN 1538-4357

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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 ± 30M_ yr−1 kpc−2, which may suggest that we are witnessing an intense period of bulge growth in these galaxies.

Item Type: Article
Schools/Departments: University of Nottingham, UK > Faculty of Science > School of Physics and Astronomy
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Depositing User: Eprints, Support
Date Deposited: 06 Oct 2017 13:31
Last Modified: 04 May 2020 17:00

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