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

Husemann, B., Davis, Timothy ORCID:, 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: 02 May 2023 19:19

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