Aravena, M. and Bertoldi, F. and Schinnerer, E. and Weiss, A. and Jahnke, K. and Carilli, C. L. and Frayer, D. and Henkel, C. and Brusa, M. and Menten, K. M. and Salvato, M. and Smolcic, V. (2008) Properties of the molecular gas in a starbursting QSO at z = 1.83 in the COSMOS field. Astronomy and Astrophysics, 491 (1). pp. 173-181. ISSN 0004-6361 http://resolver.caltech.edu/CaltechAUTHORS:ARAaanda08
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Using the IRAM 30 m telescope, we have detected the 12CO J = 2−1, 4−3, 5−4, and 6−5 emission lines in the millimeter-bright, blank-field selected AGN COSMOS J100038+020822 at redshift z = 1.8275. The sub-local thermodynamic equilibrium (LTE) excitation of the J = 4 level implies that the gas is less excited than that in typical nearby starburst galaxies such as NGC 253, and in the high-redshift quasars studied to date, such as J1148+5251 or BR1202-0725. Large velocity gradient (LVG) modeling of the CO line spectral energy distribution (CO SED; flux density vs. rotational quantum number) yields H2 densities in the range 10^3.5−10^4.0 cm^−3, and kinetic temperatures between 50 K and 200 K. The H2 mass of (3.6−5.4) × 10^10 M☉ implied by the line intensities compares well with our estimate of the dynamical mass within the inner 1.5 kpc of the object. Fitting a two-component gray body spectrum, we find a dust mass of 1.2× 10^9 M☉, and cold and hot dust temperatures of 42±5 K and 160± 25 K, respectively. The broad MgII line allows us to estimate the mass of the central black hole as 1.7 × 10^9 M☉. Although the optical spectrum and multi-wavelength SED matches those of an average QSO, the molecular gas content and dust properties resemble those of known submillimeter galaxies (SMGs). The optical morphology of this source shows tidal tails that suggest a recent interaction or merger. Since it shares properties of both starburst and AGN, this object appears to be in a transition from a strongly starforming submillimeter galaxy to a QSO.
|Additional Information:||© ESO 2008. Article published by EDP Sciences. Received 17 July 2008 / Accepted 4 September 2008. Manuel Aravena was supported for this research through a stipend from the International Max Planck Research School (IMPRS) for Radio and Infrared Astronomy at the Universities of Bonn and Cologne. This work is based on observations with 30m telescope of the Institute for Radioastronomy at Millimeter Wavelengths (IRAM), which is funded by the German Max Planck Society, the French CNRS and the Spanish National Geographical Institute. Also based on observations with the Very Large Array of the National Radio Astronomy Observatory, which is a facility of the National Science Foundation, operated under cooperative agreement by Associated Univ. Inc. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc, under NASA contract NAS 5-26555; also based on data collected at: the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan; the XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA; the European Southern Observatory, Chile; Kitt Peak National Observatory, Cerro Tololo Inter-American Observatory, and the National Optical Astronomy Observatory, which are operated by the Association of Universities for Research in Astronomy Inc. (AURA) under cooperative agreement with the National Science Foundation; and the Canada-France-Hawaii Telescope operated by the National Research Council of Canada, the Centre National de la Recherche Scientifique de France and the University of Hawaii.|
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|Deposited On:||23 Dec 2008 01:03|
|Last Modified:||26 Dec 2012 10:40|
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