Cold dust emission from X-ray AGN in the SCUBA-2 Cosmology Legacy Survey: dependence on luminosity, obscuration and AGN activity

Manda Banerji, R. G. McMahon, C. J. Willott, J. E. Geach, C. M. Harrison, S. Alaghband-Zadeh, D. M. Alexander, N. Bourne, K. E. K. Coppin, J. S. Dunlop, D. Farrah, M. Jarvis, M. J. Michałowski, M. Page, D. J. B. Smith, A. M. Swinbank, M. Symeonidis, P. P. van der Werf

Research output: Contribution to journalArticlepeer-review


We study the 850-μm emission in X-ray-selected active galactic nuclei (AGN) in the ˜2 deg2 COSMOS field using new data from the SCUBA-2 Cosmology Legacy Survey. We find 19 850-μm bright X-ray AGN in a `high-sensitivity' region covering 0.89 deg2 with flux densities of S850 = 4-10 mJy. The 19 AGN span the full range in redshift and hard X-ray luminosity covered by the sample - 0.7 ≲ z ≲ 3.5 and 43.2 ≲ log10(LX) ≲ 45. We report a highly significant stacked 850-μm detection of a hard X-ray flux-limited population of 699 z > 1 X-ray AGN - S850 = 0.71 ± 0.08 mJy. We explore trends in the stacked 850-μm flux densities with redshift, finding no evolution in the average cold dust emission over the redshift range probed. For type 1 AGN, there is no significant correlation between the stacked 850-μm flux and hard X-ray luminosity. However, in type 2 AGN the stacked submillimeter flux is a factor of 2 higher at high luminosities. When averaging over all X-ray luminosities, no significant differences are found in the stacked submillimeter fluxes of type 1 and type 2 AGN as well as AGN separated on the basis of X-ray hardness ratios and optical-to-infrared colours. However, at log10(L2 - 10/erg s-1) > 44.4, dependences in average submillimeter flux on the optical-to-infrared colours become more pronounced. We argue that these high-luminosity AGN represent a transition from a secular to a merger-driven evolutionary phase where the star formation rates and accretion luminosities are more tightly coupled. Stacked AGN 850-μm fluxes are compared to the stacked fluxes of a mass-matched sample of K-band-selected non-AGN galaxies. We find that at 10.5
Original languageEnglish
Pages (from-to)419-438
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Publication statusPublished - 1 Nov 2015


  • quasars: general
  • X-rays: galaxies
  • galaxies: evolution
  • submillimetre: galaxies


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