Evidence for feedback in action from the molecular gas content in the z ~ 1.6 outflowing QSO XID2028
Journal
Date Issued
2015
Author(s)
Brusa, M.
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Mainieri, V.
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Perna, M.
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Merloni, A.
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Lutz, D.
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Maiolino, R.
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Rosario, D.
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Daddi, E.
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Lusso, E.
Description
Based on observations carried out under project number X–8 with the IRAM PdBI. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). We gratefully acknowledge the allocation of IRAM DDT time, and we thank the staff of the IRAM Observatory for their support of this program. M.B., M.P., and G.L. acknowledge support from the FP7 Career Integration Grant “eEASy” (“SMBH evolution through cosmic time: from current surveys to eROSITA-Euclid AGN Synergies”, CIG 321913). M.B. gratefully acknowledges fundings from the DFG cluster of excellence “Origin and Structure of the Universe” ( www.universe-cluster.de ). We acknowledge financial support from INAF under the contracts PRIN-INAF-2011 (“Black Hole growth and AGN feedback through cosmic time”), PRIN-INAF-2012 (“The Lifecycle of early Black Holes”) and PRIN MIUR 2010-2011 (“The dark Universe and the cosmic evolution of baryons”). We thank Dennis Downes and Andrea Comastri for enlightening discussions. We thank the anonymous referee for his/her interest in the results of our work, a very careful reading of the paper, and useful suggestions that improved the presentation of the results.
Abstract
Aims: Gas outflows are believed to play a pivotal role in shaping galaxies, as they regulate both star formation and black hole growth. Despite their ubiquitous presence, the origin and the acceleration mechanism of these powerful and extended winds is not yet understood. Direct observations of the cold gas component in objects with detected outflows at other wavelengths are needed to assess the impact of the outflow on the host galaxy interstellar medium (ISM).
Methods: We observed with the Plateau de Bure Interferometer an obscured quasar at z ~ 1.5, XID2028, for which the presence of an ionized outflow has been unambiguously signalled by NIR spectroscopy. The detection of 12CO(3-2) emission in this source allows us to infer the molecular gas content and compare it to the ISM mass derived from the dust emission. We then analyzed the results in the context of recent insights on scaling relations, which describe the gas content of the overall population of star-forming galaxies at a similar redshifts.
Results: The star formation efficiency (~100) and gas mass (Mgas = 2.1-9.5 × 1010 M☉) inferred from the CO(3-2) line depend on the underlying assumptions on the excitation of the transition and the CO-to-H2 conversion factor. However, the combination of this information and the ISM mass estimated from the dust mass suggests that the ISM/gas content of XID2028 is significantly lower than expected for its observed M⋆, sSFR and redshift, based on the most up-to-date calibrations (with gas fraction <20% and depletion timescale <340 Myr).
Conclusions: Overall, the constraints we obtain from the far infrared and millimeter data suggest that we are observing QSO feedback able to remove the gas from the host. Based on observations with the Plateau de Bure millimetre interferometer, operated by the Institute for Radio Astronomy in the Millimetre Range (IRAM), which is funded by a partnership of INSU/CNRS (France), MPG (Germany) and IGN (Spain).A FITS file for the spectrum shown in Fig. 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A11
Methods: We observed with the Plateau de Bure Interferometer an obscured quasar at z ~ 1.5, XID2028, for which the presence of an ionized outflow has been unambiguously signalled by NIR spectroscopy. The detection of 12CO(3-2) emission in this source allows us to infer the molecular gas content and compare it to the ISM mass derived from the dust emission. We then analyzed the results in the context of recent insights on scaling relations, which describe the gas content of the overall population of star-forming galaxies at a similar redshifts.
Results: The star formation efficiency (~100) and gas mass (Mgas = 2.1-9.5 × 1010 M☉) inferred from the CO(3-2) line depend on the underlying assumptions on the excitation of the transition and the CO-to-H2 conversion factor. However, the combination of this information and the ISM mass estimated from the dust mass suggests that the ISM/gas content of XID2028 is significantly lower than expected for its observed M⋆, sSFR and redshift, based on the most up-to-date calibrations (with gas fraction <20% and depletion timescale <340 Myr).
Conclusions: Overall, the constraints we obtain from the far infrared and millimeter data suggest that we are observing QSO feedback able to remove the gas from the host. Based on observations with the Plateau de Bure millimetre interferometer, operated by the Institute for Radio Astronomy in the Millimetre Range (IRAM), which is funded by a partnership of INSU/CNRS (France), MPG (Germany) and IGN (Spain).A FITS file for the spectrum shown in Fig. 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/578/A11
Volume
578
Start page
A11
Issn Identifier
0004-6361
Ads BibCode
2015A&A...578A..11B
Rights
open.access
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