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The evolutionary connection between QSOs and SMGs: Molecular gas in far-infrared luminous QSOs at z∼2.5

Lookup NU author(s): Dr Christopher HarrisonORCiD


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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 L FIR, 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 (∼1Myr) but ubiquitous phase in the transformation of dust-obscured, gas-rich, starburst-dominated SMGs into unobscured, gas-poor, QSOs. © 2012 The Authors Monthly Notices of the Royal Astronomical Society © 2012 RAS.

Publication metadata

Author(s): Simpson JM, Smail I, Swinbank AM, Alexander DM, Auld R, Baes M, Bonfield DG, Clements DL, Cooray A, Coppin KEK, Danielson ALR, Dariush A, Dunne L, de Zotti G, Harrison CM, Hopwood R, Hoyos C, Ibar E, Ivison RJ, Jarvis MJ, Lapi A, Maddox SJ, Page MJ, Riechers DA, Valiante E, van der Werf PP

Publication type: Article

Publication status: Published

Journal: Monthly Notices of the Royal Astronomical Society

Year: 2012

Volume: 426

Issue: 4

Pages: 3201-3210

Print publication date: 11/11/2012

Online publication date: 11/11/2012

ISSN (print): 0035-8711

ISSN (electronic): 1365-2966

Publisher: Oxford University Press


DOI: 10.1111/j.1365-2966.2012.21941.x


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