The Herschel -SPIRE Dark Field III: probing the deepest Herschel field with SCUBA-2

Journal article

The Herschel-SPIRE Dark Field (SDF), originally observed for calibration of the SPIRE instrument, is the deepest far-infrared field to date (equivalent exposure time of h deg) at wavelengths 250–m, probing below the SPIRE confusion limit. We present SCUBA-2 m observations covering the central Deep Region, detecting 36 sources with number counts consistent with previous surveys at this wavelength. Cross-identification with multiwavelength catalogues reveals 20 SPIRE-dropouts, whose stacked SPIRE fluxes suggest a photometric redshift of . Photo-z estimates from the magphys, bagpipes, and mmpz tools are consistent within the uncertainties for 3 sources (–2), while 13 are inconsistent, and 20 lack sufficient data due to counterpart ambiguity or non-detections. We flag a total of 9 sources as potentially lensed and 15 as potential multiples. Spectral energy distribution fitting yields average properties for SPIRE-detected sources of log/L, log/M, and SFR M yr. The stacked dropouts yield log/L, log/M, and SFR M yr at a derived (at a fixed ) contributing () per cent of the cosmic star formation rate density (SFRD) at that epoch. We find an excess at in the SFRD of SPIRE-detected sources, consistent with the sub-mJy bump in SPIRE number counts previously identified in this field, possibly tracing large-scale structure.

Authors: Parmar, A; Clements, DL; Pearson, C; Varnish, TWO

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 548
• Issue: 3
• Pages: stag631
• Article number: stag631
• Publication date: 2026-04-02
• Acceptance date: 2026-03-24
• DOI: 10.1093/mnras/stag631
• EISSN: 1365-2966
• ISSN: 0035-8711
• Language: English
• Keywords: galaxies: high-redshift; submillimetre: galaxies; galaxies: photometry; galaxies: evolution; cosmology: observations