Water Vapor Emission Reveals a Highly Obscured, Star-forming Nuclear Region in the QSO Host Galaxy APM 08279+5255 at z = 3.9
Abstract
We present the detection of four rotational emission lines of water vapor, from energy levels E_u/k = 101-454 K, in the gravitationally lensed z = 3.9 QSO host galaxy APM 08279+5255. While the lowest H_2O lines are collisionally excited in clumps of warm, dense gas (density of hydrogen nuclei n_H =(3.1 ± 1.2) x 10^6 cm^-3, gas temperature T_g ~ 105 ± 21 K), we find that the excitation of the higher lines is dominated by the intense local infrared radiation field. Since only collisionally excited emission contributes to gas cooling, we conclude that H2O is not a significant coolant of the warm molecular gas. Our excitation model requires the radiatively excited gas to be located in an extended region of high 100 μm opacity (τ_(100) = 0.9 ± 0.2). Locally, such extended infrared-opaque regions are found only in the nuclei of ultraluminous infrared galaxies. We propose a model where the infrared-opaque circumnuclear cloud, which is penetrated by the X-ray radiation field of the QSO nucleus, contains clumps of massive star formation where the H_2O emission originates. The radiation pressure from the intense local infrared radiation field exceeds the thermal gas pressure by about an order of magnitude, suggesting close to Eddington-limited star formation in these clumps.
Additional Information
© 2011 The American Astronomical Society. Received 2011 June 23; accepted 2011 September 2; published 2011 October 21. This work is based on observations carried out with the IRAM Plateau de Bure Interferometer. IRAM is supported by INSU/CNRS (France),MPG (Germany) and IGN (Spain). D.R. acknowledges support from NASA through a Spitzer grant. We thank Melanie Krips for expert assistance with the IRAM data reduction and Rodrigo Ibata for providing the NICMOS image used in Figure 1.We also thank Xander Tielens for commenting on an earlier version of this Letter. Facility: IRAM:InterferometerAttached Files
Published - vanderWerf2011p16477Astrophys_J_Lett.pdf
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Additional details
- Eprint ID
- 28462
- Resolver ID
- CaltechAUTHORS:20111214-093211915
- Institut national des sciences de l'Univers (INSU)
- Max Planck Gesellschaft
- Instituto Geográfico Nacional (IGN)
- NASA
- Centre National de la Recherche Scientifique (CNRS)
- Created
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2011-12-14Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field