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ALMA resolves extended star formation in high-z AGN host galaxies.

Harrison, C.M. and Simpson, J.M. and Stanley, F. and Alexander, D.M. and Daddi, E. and Mullaney, J.R. and Pannella, M. and Rosario, D.J. and Smail, I. (2016) 'ALMA resolves extended star formation in high-z AGN host galaxies.', Monthly notices of the Royal Astronomical Society : letters., 457 (1). L122-L126.


We present high-resolution (0.3 arcsec) Atacama Large Millimeter Array (ALMA) 870 μm imaging of five z ≈ 1.5–4.5 X-ray detected AGN (with luminosities of L2–8keV > 1042 erg s−1). These data provide a ≳20 times improvement in spatial resolution over single-dish rest-frame far-infrared (FIR) measurements. The sub-millimetre emission is extended on scales of FWHM ≈ 0.2 arcsec–0.5 arcsec, corresponding to physical sizes of 1–3 kpc (median value of 1.8 kpc). These sizes are comparable to the majority of z=1–5 sub-millimetre galaxies (SMGs) with equivalent ALMA measurements. In combination with spectral energy distribution analyses, we attribute this rest-frame FIR emission to dust heated by star formation. The implied star-formation rate surface densities are ≈20–200 M⊙ yr−1 kpc−2, which are consistent with SMGs of comparable FIR luminosities (i.e. LIR ≈ [1–5] × 1012 L⊙). Although limited by a small sample of AGN, which all have high-FIR luminosities, our study suggests that the kpc-scale spatial distribution and surface density of star formation in high-redshift star-forming galaxies is the same irrespective of the presence of X-ray detected AGN.

Item Type:Article
Keywords:Galaxies: active, Galaxies: evolution, Quasars: general, Galaxies: star formation, Submillimetre: galaxies.
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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society: Letters ©: 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:04 January 2016
Date deposited:22 February 2016
Date of first online publication:01 February 2016
Date first made open access:22 February 2016

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