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Integral field spectroscopy of nearby QSOs II. The molecular gas content and condition for star formation

Husemann, B., Davis, Timothy, Jahnke, K., Dannerbauer, H., Urrutia, T. and Hodge, J. 2017. Integral field spectroscopy of nearby QSOs II. The molecular gas content and condition for star formation. Monthly Notices of the Royal Astronomical Society 470 (2) , pp. 1570-1586. 10.1093/mnras/stx1123

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We present single-dish 12CO(1 − 0) and 12CO(2 − 1) observations for 14 low-redshift quasi-stellar objects (QSOs). In combination with optical integral field spectroscopy we study how the cold gas content relates to the star formation rate (SFR) and black hole accretion rate. 12CO(1 − 0) is detected in 8 of 14 targets and 12CO(2 − 1) is detected in 7 out of 11 cases. The majority of disc-dominated QSOs reveal gas fractions and depletion times well matching normal star forming systems. Two gas-rich major mergers show clear starburst signatures with higher than average gas fractions and shorter depletion times. Bulge-dominated QSO hosts are mainly undetected in 12CO(1 − 0) which corresponds, on average, to lower gas fractions than in disc-dominated counterparts. Their SFRs however imply shorter than average depletion times and higher star formation efficiencies. Negative QSO feedback through removal of cold gas seems to play a negligible role in our sample. We find a trend between black hole accretion rate and total molecular gas content for disc-dominated QSOs when combined with literature samples. We interpret this as an upper envelope for the nuclear activity and is well represented by a scaling relation between the total and circum-nuclear gas reservoir accessible for accretion. Bulge-dominated QSOs significantly differ from that scaling relation and appear uncorrelated with the total molecular gas content. This could be explained either by a more compact gas reservoir, blow out of the gas envelope through outflows, or a different ISM phase composition.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: Galaxies: active, quasars: emission-lines, Galaxies: ISM, Galaxies: star formation
Publisher: Oxford University Press
ISSN: 0035-8711
Funders: STFC
Date of First Compliant Deposit: 14 June 2017
Date of Acceptance: 5 May 2017
Last Modified: 20 Dec 2017 15:19

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