The nature of 500 micron risers – II. Multiplicities and environments of sub-mm faint dusty star-forming galaxies. Issue 1 (28th November 2022)

• Record Type: Journal Article
• Authors: Cairns, J; Clements, D L; Greenslade, J; Petitpas, G; Cheng, T; Ding, Y; Parmar, A; Pérez-Fournon, I; Riechers, D
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 519:Issue 1(2023)
• Page Start: 709
• Page End: 728
• Publication Date: 2022-11-28
• Subjects: galaxies: high-redshift -- galaxies: starburst -- infrared: galaxies -- submillimetre: galaxies; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac3486
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We present Submillimeter Common User Bolometer Array 2 (SCUBA-2) and Submillimeter Array (SMA) follow-up observations of four candidate high-redshift dusty star-forming galaxies, selected as sources with rising spectral energy distributions in the 250, 350, and 500 μ m Herschel SPIRE bands. Previous SMA observations showed no counterparts to these sources, but in our deeper sub-mm observations we detect counterparts to all four 500 μ m risers, with three resolving into multiple systems. For these three multiple systems, the SMA 345 GHz (≈870 μ m) observations recover $123 \pm 73{{\ \rm per\ cent}}$, $60 \pm 15{{\ \rm per\ cent}}$, and $19 \pm 4{{\ \rm per\ cent}}$ of the integrated 850 μ m flux density from SCUBA-2, indicating that there may be additional sources below our SMA detection limit making up a dense, protocluster core. The fourth 500 μ m riser was observed at a lower frequency and so we cannot make a similar comparison. We estimate photometric redshifts based on FIR/sub-mm colours, finding that three fourths likely lie at z ≥ 2. This fits with the interpretation that the 500 μ m riser selection criterion selects both intrinsically red, individual galaxies at z > 4, and multiple systems at more moderate redshifts, artificially reddened by the effects of blending. We use the SCUBA-2 850 μ m maps to investigate the environments of these 500 μ m risers. By constructing cumulative number counts and estimating photometric redshifts for surrounding SCUBA-2 detections, we find that one of our 500 μ m risers could plausibly reside in a z ≥ 2 protocluster. We infer that bright 500 μ m risers with faint 850 μ m flux densities are typically multiple systems at z ≥ 2 that may reside in overdensities of bright sub-mm galaxies.