We present a comprehensive study of the molecular gas properties of 17 Type 2 quasars at z < 0.2 from the Quasar Feedback Survey (L$_{\rm [O~{\small III}]}$ > 1042.1 $\rm ergs^{-1}$), 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.
We present a pilot, untargeted extragalactic carbon monoxide (CO) emission-line survey using ALMACAL, a project utilizing ALMA calibration data for scientific purposes. In 33 deep (Texp > 40 min) ALMACAL fields, we report six CO emission-line detections above S/N > 4, one-third confirmed by MUSE observations. With this pilot survey, we probe a cosmologically significant volume of ∼105 cMpc3, widely distributed over many pointings in the southern sky, making the survey largely insusceptible to the effects of cosmic variance. We derive the redshift probability of the CO detections using probability functions from the Shark semi-analytical model of galaxy formation. By assuming typical CO excitations for the detections, we put constraints on the cosmic molecular gas mass density evolution over the redshift range 0 < z < 1.5. The results of our pilot survey are consistent with the findings of other untargeted emission-line surveys and the theoretical model predictions and currently cannot rule out a non-evolving molecular gas mass density. Our study demonstrates the potential of using ALMA calibrator fields as a multi-sightline untargeted CO emission-line survey. Applying this approach to the full ALMACAL database will provide an accurate, free of cosmic variance, measurement of the molecular luminosity function as a function of redshift.
more » « less- NSF-PAR ID:
- 10386405
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Monthly Notices of the Royal Astronomical Society
- Volume:
- 519
- Issue:
- 1
- ISSN:
- 0035-8711
- Format(s):
- Medium: X Size: p. 34-49
- Size(s):
- ["p. 34-49"]
- Sponsoring Org:
- National Science Foundation
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