An ALMA survey of the SCUBA-2 CLS UDS field: physical properties of 707 sub-millimetre galaxies

U. Dudzevičiūtė, Ian Smail, A. M. Swinbank, S. M. Stach, O. Almaini, E. da Cunha, Fang Xia An, V. Arumugam, J. Birkin, A. W. Blain, S. C. Chapman, C. J. Conselice, K. E. K. Coppin, J. S. Dunlop, D. Farrah, J. E. Geach, B. Gullberg, W. G. Hartley, J. A. Hodge, R. J. IvisonD. T. Maltby, D. Scott, C. J. Simpson, F. Walter, J. L. Wardlow, A. Weiss, P. van der Werf

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We analyse the physical properties of a large, homogeneously selected sample of ALMA-located sub-mm galaxies (SMGs) detected in the SCUBA-2 CLS 850-$\mu$m map of the UKIDSS/UDS field. This survey, AS2UDS, identified 707 SMGs across the ~1 sq.deg. field, including ~17 per cent which are undetected in the optical/near-infrared to $K$>~25.7 mag. We interpret the UV-to-radio data using a physically motivated model, MAGPHYS and determine a median photometric redshift of z=2.61+-0.08, with a 68th percentile range of z=1.8-3.4 and just ~6 per cent at z>4. The redshift distribution is well fit by a model combining evolution of the gas fraction in halos with the growth of halo mass past a threshold of ~4x10$^{12}$M$_\odot$, thus SMGs may represent the highly efficient collapse of gas-rich massive halos. Our survey provides a sample of the most massive, dusty galaxies at z>~1, with median dust and stellar masses of $M_d$=(6.8+-0.3)x10$^{8}$M$_\odot$ (thus, gas masses of ~10$^{11}$M$_\odot$) and $M_\ast=$(1.26+-0.05)x10$^{11}$M$_\odot$. These galaxies have gas fractions of $f_{gas}=$0.41+-0.02 with depletion timescales of ~150Myr. The gas mass function evolution at high masses is consistent with constraints at lower masses from blind CO-surveys, with an increase to z~2-3 and then a decline at higher redshifts. The space density and masses of SMGs suggests that almost all galaxies with $M_\ast$>~2x10$^{11}$M$_\odot$ have passed through an SMG-like phase. We find no evolution in dust temperature at a constant far-infrared luminosity across z~1.5-4. We show that SMGs appear to behave as simple homologous systems in the far-infrared, having properties consistent with a centrally illuminated starburst. Our study provides strong support for an evolutionary link between the active, gas-rich SMG population at z>1 and the formation of massive, bulge-dominated galaxies across the history of the Universe.
Original languageEnglish
Article numberstaa769
Pages (from-to)3828–3860
Number of pages33
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
Early online date2 Apr 2020
Publication statusPublished - May 2020


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