An ALMA survey of the SCUBA-2 Cosmology Legacy Survey UKIDSS/UDS field: Source catalogue and properties

Stach, S. M. and Dudzevičiūtė, U. and Smail, I. and Swinbank, A. M. and Geach, J. E. and Simpson, J. M. and An, F. X. and Almaini, O. and Arumugam, V. and Blain, A. W. and Chapman, S. C. and Chen, C.-C. and Conselice, C. J. and Cooke, E. A. and Coppin, K. E. K. and da Cunha, E. and Dunlop, J. S. and Farrah, D. and Gullberg, B. and Hodge, J. A. and Ivison, R. J. and Kocevski, Dale D. and Michałowski, M. J. and Miyaji, Takamitsu and Scott, D. and Thomson, A. P. and Wardlow, J. L. and Weiss, Axel and van der Werf, P. (2019) An ALMA survey of the SCUBA-2 Cosmology Legacy Survey UKIDSS/UDS field: Source catalogue and properties. Monthly Notices of the Royal Astronomical Society, 487 (4). pp. 4648-4668. ISSN 0035-8711

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Abstract

We present the catalogue and properties of sources in AS2UDS, an870-$\mu$m continuum survey with the Atacama LargeMillimetre/sub-millimetre Array (ALMA) of 716 single-dish sub-millimetresources detected in the UKIDSS/UDS field by the SCUBA-2 Cosmology LegacySurvey. In our sensitive ALMA follow-up observations we detect 708sub-millimetre galaxies (SMGs) at $>$\,4.3$\sigma$ significanceacross the $\sim$\,1-degree diameter field. We combine our precise ALMApositions with the extensive multi-wavelength coverage in the UDS fieldto fit the spectral energy distributions of our SMGs to derive a medianredshift of $z_{\rm phot}=$\,2.61$\pm$0.09. This large sample reveals astatistically significant trend of increasing sub-millimetre flux withredshift suggestive of galaxy downsizing. 101 ALMA maps do not show a$>$\,4.3$\sigma$ SMG, but we demonstrate from stacking {\it Herschel}SPIRE observations at these positions, that the vast majority of theseblank maps correspond to real single-dish sub-millimetre sources. Wefurther show that these blank maps contain an excess of galaxies at$z_{\rm phot}=$\,1.5--4 compared to random fields, similar to theredshift range of the ALMA-detected SMGs. In addition, we combine X-rayand mid-infrared active galaxy nuclei activity (AGN) indicators to yielda likely range for the AGN fraction of 8--28\,\% in our sample. Finally,we compare the redshifts of this population of high-redshift, stronglystar-forming galaxies with the inferred formation redshifts of massive,passive galaxies being found out to $z\sim$\,2, finding reasonableagreement -- in support of an evolutionary connection between these twoclasses of massive galaxy.