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The evolutionary connection between QSOs and SMGs: molecular gas in far-infrared luminous QSOs at z \tilde 2.5.

Simpson, J.M. and Smail, I. and Swinbank, A.M. and Alexander, D.M. and Auld, R. and Baes, M. and Bonfield, D.G. and Clements, D.L. and Cooray, A. and Coppin, K.E.K. and Danielson, A.L.R. and Dariush, A. and Dunne, L. and de Zotti, G. and Harrison, C.M. and Hopwood, R. and Hoyos, C. and Ibar, E. and Ivison, R.J. and Jarvis, M.J. and Lapi, A. and Maddox, S.J. and Page, M.J. and Riechers, D.A. and Valiante, E. and van der Werf, P.P. (2012) 'The evolutionary connection between QSOs and SMGs: molecular gas in far-infrared luminous QSOs at z \tilde 2.5.', Monthly notices of the Royal Astronomical Society., 426 (4). pp. 3201-3210.


We present Institut de Radioastronomie Millimétrique Plateau de Bure Interferometer observations of the 12CO (3–2) emission from two far-infrared luminous QSOs at z ∼ 2.5 selected from the Herschel-Astrophysical Tetrahertz Large Area Survey. These far-infrared bright QSOs were selected to have supermassive black holes (SMBHs) with masses similar to those thought to reside in submillimetre galaxies (SMGs) at z ∼ 2.5, making them ideal candidates as systems in the potential transition from an ultraluminous infrared galaxy phase to a submillimetre faint, unobscured, QSO. We detect 12CO (3–2) emission from both QSOs and we compare their baryonic, dynamical and SMBH masses to those of SMGs at the same epoch. We find that these far-infrared bright QSOs have similar dynamical but lower gas masses than SMGs. We combine our results with literature values and find that at a fixed LFIR, far-infrared bright QSOs have ∼50 ± 30 per cent less warm/dense gas than SMGs. Taken together with previous results, which show that QSOs lack the extended, cool reservoir of gas seen in SMGs, this suggests that far-infrared bright QSOs are at a different evolutionary stage. This is consistent with the hypothesis that far-infrared bright QSOs represent a short (∼1 Myr) but ubiquitous phase in the transformation of dust-obscured, gas-rich, starburst-dominated SMGs into unobscured, gas-poor, QSOs.

Item Type:Article
Keywords:Galaxies, Evolution, Formation, Quasars, Emission lines, J0908−0034, J0911+0027.
Full text:(NA) Not Applicable
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Date accepted:No date available
Date deposited:No date available
Date of first online publication:November 2012
Date first made open access:No date available

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