Volume 613, May 2018
|Number of page(s)||11|
|Published online||28 May 2018|
ALMA view of RX J1131-1231: Sub-kpc CO (2-1) mapping of a molecular disk in a lensed star-forming quasar host galaxy
Institute of Physics, Laboratory of Astrophysics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Observatoire de Sauverny,
2 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
3 Max Planck Institute for Astrophysics, Karl-Schwarzschild-Strasse 1, 85740 Garching, Germany
4 Kapteyn Astronomical Institute, University of Groningen, PO Box 800, 9700 AV Groningen, The Netherlands
5 ASTRON, Netherlands Institute for Radio Astronomy, PO Box 2, 7990 AA Dwingeloo, The Netherlands
6 STAR Institute, Quartier Agora, Allée du six Août 19c, 4000 Liège, Belgium
7 Department of Physics, University of California, Davis, CA 95616, USA
8 Physik-Department, Technische Universität München, James-Franck-Strasse 1, 85748 Garching, Germany
9 Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, Taipei 10617, Taiwan
10 Observatoire de Genève, Université de Genève, 51 Chemin des Maillettes, 1290 Versoix, Switzerland
Accepted: 12 December 2017
We present ALMA 2-mm continuum and CO (2-1) spectral line imaging of the gravitationally lensed z = 0.654 star-forming/quasar composite RX J1131-1231 at 240–400 mas angular resolution. The continuum emission is found to be compact and coincident with the optical emission, whereas the molecular gas forms a complete Einstein ring, which shows strong differential magnification. The de-lensed source structure is determined on 400-parsec-scales resolution using a Bayesian pixelated visibility-fitting lens modelling technique. The reconstructed molecular gas velocity-field is consistent with a large rotating disk with a major-axis FWHM ~9.4 kpc at an inclination angle of i = 54° and with a maximum rotational velocity of 280 km s−1. From dynamical model fitting we find an enclosed mass within 5 kpc of M(r < 5 kpc) = (1.46 ± 0.31) × 1011 M⊙. The molecular gas distribution is highly structured, with clumps that are co-incident with higher gas velocity dispersion regions (40–50 km s−1) and with the intensity peaks in the optical emission, which are associated with sites of on-going turbulent star-formation. The peak in the CO (2-1) distribution is not co-incident with the AGN, where there is a paucity of molecular gas emission, possibly due to radiative feedback from the central engine. The intrinsic molecular gas luminosity is L′CO = 1.2 ± 0.3 × 1010 K km s−1 pc2 and the inferred gas mass is MH2 = 8.3 ± 3.0 × 1010 M⊙, which given the dynamical mass of the system is consistent with a CO–H2 conversion factor of α = 5.5 ± 2.0 M⊙ (K km s−1 pc2)−1. This suggests that the star-formation efficiency is dependent on the host galaxy morphology as opposed to the nature of the AGN. The far-infrared continuum spectral energy distribution shows evidence for heated dust, equivalent to an obscured star-formation rate of SFR = 69−25+41 × (7.3/μIR) M⊙ yr−1, which demonstrates the composite star-forming and AGN nature of this system.
Key words: galaxies: starburst / galaxies: ISM / galaxies: high-redshift / galaxies: star formation / submillimeter: galaxies / techniques: high angular resolution
© ESO 2018
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.