An ALMA survey of CO in submillimetre galaxies: companions, triggering, and the environment in blended sources

Wardlow, J.L.; Simpson, J.M.; Smail, Ian; Swinbank, A.M.; Blain, A.W.; Brandt, W.N.; Chapman, S.C.; Chen, Chian-Chou; Cooke, E.A.; Dannerbauer, H.; Gullberg, B.; Hodge, J.A.; Ivison, R.J.; Knudsen, K.K.; Scott, Douglas; Thomson, A.P.; Weiß, A.; van der Werf, P.P.

Abstract

We present ALMA observations of the mid-J 12CO emission from six single-dish selected 870-μm sources in the Extended Chandra Deep Field-South and UKIDSS Ultra-Deep Survey fields. These six single-dish submillimetre sources were selected based on previous ALMA continuum observations, which showed that each comprised a blend of emission from two or more individual submillimetre galaxies (SMGs), separated on 5–10 arcsec scales. The six single-dish submillimetre sources targeted correspond to a total of 14 individual SMGs, of which seven have previously measured robust optical/near-infrared spectroscopic redshifts, which were used to tune our ALMA observations. We detect CO(3–2) or CO(4–3) at z = 2.3–3.7 in 7 of the 14 SMGs, and in addition serendipitously detect line emission from three gas-rich companion galaxies, as well as identify four new 3.3 mm selected continuum sources in the six fields. Joint analysis of our CO spectroscopy and existing data suggests that 64(±18)percent of the SMGs in blended submillimetre sources are unlikely to be physically associated. However, three of the SMG fields (50 per cent) contain new, serendipitously detected CO-emitting (but submillimetre-faint) sources at similar redshifts to the 870 μm selected SMGs we targeted. These data suggest that the SMGs inhabit overdense regions, but that these are not sufficiently overdense on ∼100 kpc scales to influence the source blending given the short lifetimes of SMGs. We find that 21±12percent of SMGs have spatially distinct and kinematically close companion galaxies (∼8–150 kpc and ≲ 300 km s−1), which may have enhanced their star formation via gravitational interactions.

Citation

Wardlow, J., Simpson, J., Smail, I., Swinbank, A., Blain, A., Brandt, W., Chapman, S., Chen, C.-C., Cooke, E., Dannerbauer, H., Gullberg, B., Hodge, J., Ivison, R., Knudsen, K., Scott, D., Thomson, A., Weiß, A., & van der Werf, P. (2018). An ALMA survey of CO in submillimetre galaxies: companions, triggering, and the environment in blended sources. Monthly Notices of the Royal Astronomical Society, 479(3), 3879-3891. https://doi.org/10.1093/mnras/sty1526

• Journal Article Type: Article
• Acceptance Date: Jun 6, 2018
• Online Publication Date: Jun 14, 2018
• Publication Date: Sep 21, 2018
• Deposit Date: Aug 23, 2018
• Publicly Available Date: Aug 23, 2018
• Journal: Monthly Notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Royal Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 479
• Issue: 3
• Pages: 3879-3891
• DOI: https://doi.org/10.1093/mnras/sty1526
• Public URL: https://durham-repository.worktribe.com/output/1321971