Cold Dust Emission from X-ray AGN in the SCUBA-2 Cosmology Legacy Survey: Dependence on Luminosity, Obscuration & AGN Activity
Van, der Werf PP
Monthly Notices of the Royal Astronomical Society
Oxford University Press
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Banerji, M., McMahon, R., Willott, C., Geach, J., Harrison, C., Alaghband-Zadeh, S., Alexander, D., et al. (2015). Cold Dust Emission from X-ray AGN in the SCUBA-2 Cosmology Legacy Survey: Dependence on Luminosity, Obscuration & AGN Activity. Monthly Notices of the Royal Astronomical Society, 454 419-438. https://doi.org/10.1093/mnras/stv1881
We study the 850µm 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 nineteen 850µm 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 Xray luminosity covered by the sample - 0.7 ~< z ~< 3.5 and 43.2 . log₁₀(LX) ~< 45. We report a highly significant stacked 850µm detection of a hard X-ray flux-limited population of 699 z > 1 X-ray AGN - S₈₅₀=0.71±0.08mJy. We explore trends in the stacked 850µm 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 850µm 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 850µm fluxes are compared to the stacked fluxes of a mass-matched sample of Kband selected non-AGN galaxies. We find that at 10.5 <log10(M∗/M⊙)< 11.5, the non-AGN 850µm fluxes are 1.5 − 2× higher than in Type 2 AGN of equivalent mass. We suggest these differences are due to the presence of massive dusty, red starburst galaxies in the K-band selected non-AGN sample, which are not present in optically selected catalogues covering a smaller area.
galaxies:active, submillimetre:galaxies, X-rays:galaxies
MB, RGM and KEKC acknowledge support from STFC. JEG thanks the Royal Society for a University Research Fellowship. NB and JSD acknowledge the support of the European Research Council via the award of an Advanced Grant, and the contribution of the EC FP7 SPACE project ASTRODEEP (Ref.No: 312725). DMA and CMH acknowledge support from STFC grant ST/I001573/1.
External DOI: https://doi.org/10.1093/mnras/stv1881
This record's URL: https://www.repository.cam.ac.uk/handle/1810/251203