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Published October 1, 2009 | Published
Journal Article Open

Imaging Atomic and Highly Excited Molecular Gas in a z = 6.42 Quasar Host Galaxy: Copious Fuel for an Eddington-limited Starburst at the End of Cosmic Reionization

Abstract

We have imaged CO(J = 7→6) and C i(^3P_2→^3P_1) emission in the host galaxy of the z = 6.42 quasar SDSS J114816.64+525150.3 (hereafter J1148+5251) through observations with the Plateau de Bure Interferometer. The region showing CO(J = 7→6) emission is spatially resolved, and its size of 5 kpc is in good agreement with earlier CO(J = 3→2) observations. In combination with a revised model of the collisional line excitation in this source, this indicates that the highly excited molecular gas traced by the CO J = 7→6 line is subthermally excited (showing only 58% ± 8% of the CO J = 3→2 luminosity), but not more centrally concentrated. We also detect Ci(^3P_2→^3P_1) emission in the host galaxy of J1148+5251, but the line is too faint to enable a reliable size measurement. From the C i(^3P_2→^3P_1) line flux, we derive a total atomic carbon mass of M_(Ci) = 1.1 ×10^7 M_⊙, which corresponds to ~5 × 10^(−4) times the total molecular gas mass. We also searched for H_2O(J_(K_aK_c) = 212→101) emission, and obtained a sensitive line luminosity limit of L'_(H_2O) < 4.4 × 10^9 K km s^(−1) pc^2, i.e., <15% of the CO(J = 3→2) luminosity. The warm, highly excited molecular gas, atomic gas and dust in this quasar host at the end of cosmic reionization maintain an intense starburst that reaches surface densities as high as predicted by (dust opacity) Eddington limited star formation over kiloparsec scales.

Additional Information

© 2009 The American Astronomical Society. Received 2008 December 28; accepted 2009 August 10; published 2009 September 9. We thank Todd Thompson, Arjen van der Wel, and Hans- Walter Rix for helpful discussions, the anonymous referee for helpful comments, and Christian Henkel for his LVG code. This research is based on observations carried out with the IRAM PdBI. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain). D.R. acknowledges support from from NASA through Hubble Fellowship grant HST-HF-01212.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. C.C. acknowledges support from the Max-Planck- Gesellschaft and the Alexander von Humboldt-Stiftung through the Max-Planck-Forschungspreis 2005. D.R. and F.W. appreciate the hospitality at the Aspen Center for Physics, where part of this manuscript was written.

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August 21, 2023
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