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

Stach, S. M.; Dudzevičiūtė, U.; Smail, I.; Swinbank, A. M.; Geach, J. E.; An, F. X.; Almaini, O.; Arumugam, V.; Blain, A. W.; Chapman, S. C.; Conselice, C. J.; Cooke, E. A.; Coppin, K. E. K.; Cunha, E. da; Dunlop, J. S.; Farrah, D.; Gullberg, B.; Hodge, J. A.; Ivison, R. J.; Kocevski, Dale D.; Michałowski, M. J.; Miyaji, Takamitsu; Scott, D.; Wardlow, J. L.; Weiss, Axel; Werf, P. van der

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Author

Stach, S. M.

Dudzevičiūtė, U.

Smail, I.

Swinbank, A. M.

Geach, J. E.

An, F. X.

Almaini, O.

Arumugam, V.

Blain, A. W.

Chapman, S. C.

Conselice, C. J.

Cooke, E. A.

Coppin, K. E. K.

Cunha, E. da

Dunlop, J. S.

Farrah, D.

Gullberg, B.

Hodge, J. A.

Ivison, R. J.

Kocevski, Dale D.

Michałowski, M. J.

Miyaji, Takamitsu

Scott, D.

Wardlow, J. L.

Weiss, Axel

Werf, P. van der

Abstract

We present the catalogue and basic properties of sources in AS2UDS, an 870-\mum continuum survey with the Atacama Large Millimetre/sub-millimetre Array (ALMA) of 716 single-dish sub-millimetre sources detected in the UKIDSS/UDS field by the SCUBA-2 Cosmology Legacy Survey. In our sensitive ALMA follow-up observations, we detect 708 sub-millimetre galaxies (SMGs) at >4.3σ significance across the ∼1°-diameter field. We combine our precise ALMA positions with the extensive multiwavelength coverage in the UDS field which yields spectral energy distributions for our SMGs and a median redshift of z phot = 2.61 ± 0.09. This large sample reveals a statistically significant trend of increasing sub-millimetre flux with redshift suggestive of galaxy downsizing. 101 ALMA maps do not show a > 4.3σ SMG, but we demonstrate from stacking Herschel SPIRE observations at these positions, that the vast majority of these blank maps correspond to real single-dish sub-millimetre sources. We further show that these blank maps contain an excess of galaxies at z phot = 1.5-4 compared to random fields, similar to the redshift range of the ALMA-detected SMGs. In addition, we combine X-ray and mid-infrared active galaxy nuclei activity (AGN) indicators to yield a likely range for the AGN fraction of 8-28 per cent in our sample. Finally, we compare the redshifts of this population of high-redshift, strongly star-forming galaxies with the inferred formation redshifts of massive, passive galaxies being found out to z ∼ 2, finding reasonable agreement - in support of an evolutionary connection between these two classes of massive galaxy.