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The Quasar Feedback Survey: characterizing CO excitation in quasar host galaxies

Alexander, David; Calistro Rivera, G.; De Breuck, C.; Harrison, C. M.; Mainieri, V.; Lundgren, A.; Kakkad, D.; Circosta, C.; Girdhar, A.; Costa, T.; Mullaney, J. R. ; Kharb, P.; Arrigoni Battaia, F.; Farina, E. P. ; Ward, S. R. ; Silpa, S.; Smit, R.

The Quasar Feedback Survey: characterizing CO excitation in quasar host galaxies Thumbnail


G. Calistro Rivera

C. De Breuck

C. M. Harrison

V. Mainieri

A. Lundgren

D. Kakkad

C. Circosta

A. Girdhar

T. Costa

J. R. Mullaney

P. Kharb

F. Arrigoni Battaia

E. P. Farina

S. R. Ward

S. Silpa

R. Smit


We present a comprehensive study of the molecular gas properties of 17Type 2 quasars at z <0.2 from the Quasar Feedback Survey
(L[O III] > 1042.1 ergs−1), selected by their high [O III] luminosities and displaying a large diversity of radio jet properties, but
dominated by LIRG-like galaxies. With these data, we are able to investigate the impact of AGN and AGN feedback mechanisms
on the global molecular interstellar medium. Using Atacama Pathfinder EXperiment and ALMA ACA observations, we measure
the total molecular gas content using the CO(1-0) emission and homogeneously sample the carbon monoxide (CO) spectral line
energy distributions, observing CO transitions (Jup = 1, 2, 3, 6, 7). We observe high r21 ratios (r21 = L’CO(2-1)/L’CO(1-0)) with
a median r21 = 1.06, similar to local (U)LIRGs (with r21 ∼ 1) and higher than normal star-forming galaxies (with r21 ∼ 0.65).
Despite the high r21 values, for the seven targets with the required data, we find low excitation in CO(6-5) & CO(7-6) (r61 and
r62 < 0.6 in all but one target), unlike high-redshift quasars in the literature, which are far more luminous and show higher
line ratios. The ionized gas traced by [O III] exhibits systematically higher velocities than the molecular gas traced by CO. We
conclude that any effects of quasar feedback (e.g. via outflows and radio jets) do not have a significant instantaneous impact on
the global molecular gas content and excitation and we suggest that it only occurs on more localized scales.


Alexander, D., Calistro Rivera, G., De Breuck, C., Harrison, C. M., Mainieri, V., Lundgren, A., …Smit, R. (2024). The Quasar Feedback Survey: characterizing CO excitation in quasar host galaxies. Monthly Notices of the Royal Astronomical Society, 527(3), 4420–4439.

Journal Article Type Article
Acceptance Date Oct 10, 2023
Online Publication Date Oct 13, 2023
Publication Date 2024-01
Deposit Date Jan 29, 2024
Publicly Available Date Jan 29, 2024
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Royal Astronomical Society
Peer Reviewed Peer Reviewed
Volume 527
Issue 3
Pages 4420–4439
Public URL


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