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Durham University

Department of Physics

Staff profile

Publication details for Prof David Alexander

Harrison, C.M., Alexander, D.M., Mullaney, J.R. & Swinbank, A.M. (2014). Kiloparsec-scale outflows are prevalent among luminous AGN: outflows and feedback in the context of the overall AGN population. Monthly Notices of the Royal Astronomical Society 441(4): 3306-3347.

Author(s) from Durham


We present integral field unit observations covering the [O III]λλ4959, 5007 and Hβ emission lines of 16 z < 0.2 type 2 active galactic nuclei (AGN). Our targets are selected from a well-constrained parent sample of ≈24 000 AGN so that we can place our observations into the context of the overall AGN population. Our targets are radio quiet with star formation rates (SFRs; ≲[10–100] M⊙ yr−1) that are consistent with normal star-forming galaxies. We decouple the kinematics of galaxy dynamics and mergers from outflows. We find high-velocity ionized gas (velocity widths ≈600–1500 km s−1; maximum velocities ≤1700 km s−1) with observed spatial extents of ≳(6–16) kpc in all targets and observe signatures of spherical outflows and bi-polar superbubbles. We show that our targets are representative of z < 0.2, luminous (i.e. L[O III] > 1041.7 erg s−1) type 2 AGN and that ionized outflows are not only common but also in ≥70 per cent (3σ confidence) of cases, they are extended over kiloparsec scales. Our study demonstrates that galaxy-wide energetic outflows are not confined to the most extreme star-forming galaxies or radio-luminous AGN; however, there may be a higher incidence of the most extreme outflow velocities in quasars hosted in ultraluminous infrared galaxies. Both star formation and AGN activity appear to be energetically viable to drive the outflows and we find no definitive evidence that favours one process over the other. Although highly uncertain, we derive mass outflow rates (typically ≈10 times the SFRs), kinetic energies (≈0.5–10 per cent of LAGN) and momentum rates (typically ≳10–20 × LAGN/c) consistent with theoretical models that predict AGN-driven outflows play a significant role in shaping the evolution of galaxies.