THE SCUBA-2 COSMOLOGY LEGACY SURVEY: ALMA RESOLVES THE REST-FRAME FAR-INFRARED EMISSION OF SUB-MILLIMETER GALAXIES
journal contributionposted on 04.02.2016, 09:25 by J. M. Simpson, I. Smail, A. M. Swinbank, O. Almaini, Andrew William Blain, M. N. Bremer, S. C. Chapman, C-C. Chen, C. Conselice, K. E. K. Coppin, A. L. R. Danielson, J. S. Dunlop, A. C. Edge, D. Farrah, J. E. Geach, W. G. Hartley, R. J. Ivison, A. Karim, C. Lani, C-J. Ma, R. Meijerink, M. J. Michalowski, A. Mortlock, D. Scott, C. J. Simpson, M. Spaans, A. P. Thomson, E. van Kampen, P. P. van der Werf
We present high-resolution (0farcs3) 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 = 0farcs30 ± 0farcs04 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 [Superscript: 12]CO (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[Superscript: –1] kpc[Superscript: –2], which may suggest that we are witnessing an intense period of bulge growth in these galaxies.