A reassessment of the redshift distribution and physical properties of luminous (sub-)millimetre galaxies

• Published in: Monthly notices of the Royal Astronomical Society Vol. 444; no. 1; pp. 117 - 128
• Main Authors: Koprowski, M. P., Dunlop, J. S., Michałowski, M. J., Cirasuolo, M., Bowler, R. A. A.
• Format: Journal Article
• Language: English
• Published: London Oxford University Press 11.10.2014
• Subjects: Astronomy; Cosmology; Luminosity; Physical properties; Red shift; Star & galaxy formation; Antarctica, South Pole; galaxies: starburst; cosmology: observations; submillimetre: galaxies; galaxies: active; galaxies: evolution; galaxies: high-redshift
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stu1402

Motivated by the current controversy over the redshift distribution and physical properties of luminous (sub-)mm sources, we have undertaken a new study of the brightest sample of unlensed (sub-)mm sources with pre-Atacama Large Millimeter/submillimeter Array (ALMA) interferometric follow-up in the Cosmological Evolution Survey field. Exploiting the very latest multifrequency supporting data, we find that this sample displays a redshift distribution indistinguishable from that of the lensed sources uncovered with the South Pole Telescope, with z median ≃ 3.5. We also find that, over the redshift range z ≃ 2–6, the median stellar mass of the most luminous (sub-) mm sources is M * ≃ 3 × 1011 M⊙, yielding a typical specific star formation rate sSFR ≃ 3 Gyr− 1. Consistent with recent ALMA and the Submillimeter Array studies, we confirm that source blending is not a serious issue in the study of luminous (sub-) mm sources uncovered by ground-based, single-dish surveys; only ≃10–15 per cent of bright (S 850 ≃ 5–10 mJy) (sub-) mm sources arise from significant (i.e. >20 per cent) blends, and so our conclusions are largely unaffected by whether we adopt the original single-dish mm/sub-mm flux densities/positions or the interferometric data. Our results suggest that apparent disagreements over the redshift distribution of (sub-)mm sources are a result of ‘down-sizing’ in dust-enshrouded star formation, consistent with existing knowledge of the star formation histories of massive galaxies. They also indicate that extreme star-forming galaxies at high redshift are, on average, subject to the same star formation rate-limiting processes as less luminous objects, and lie on the ‘main sequence’ of star-forming galaxies at z > 3.