Get access

A new perspective on the submillimetre galaxy MM 18423+5938 at redshift 3.9296 from radio continuum imaging

Authors

  • J. P. McKean,

    Corresponding author
    1. ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, the Netherlands
    Search for more papers by this author
  • A. Berciano Alba,

    1. ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, the Netherlands
    Search for more papers by this author
  • F. Volino,

    1. Argelander-Institut für Astronomie, Auf dem Hügel 71, D-53121 Bonn, Germany
    Search for more papers by this author
  • V. Tudose,

    1. ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, the Netherlands
    2. Astronomical Institute of the Romanian Academy, Cutitul de Argint 5, RO-040557 Bucharest, Romania
    3. Research Center for Atomic Physics and Astrophysics, Atomistilor 405, RO-077125 Bucharest, Romania
    Search for more papers by this author
  • M. A. Garrett,

    1. ASTRON, Oude Hoogeveensedijk 4, 7991 PD Dwingeloo, the Netherlands
    2. Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden, the Netherlands
    3. Centre for Astrophysics and Supercomputing, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia
    Search for more papers by this author
  • A. F. Loenen,

    1. Leiden Observatory, Leiden University, Postbus 9513, 2300 RA Leiden, the Netherlands
    Search for more papers by this author
  • Z. Paragi,

    1. Joint Institute for VLBI in Europe (JIVE), Postbus 2, 7990 AA Dwingeloo, the Netherlands
    2. MTA Research Group for Physical Geodesy and Geodynamics, PO Box 91, H-1521 Budapest, Hungary
    Search for more papers by this author
  • O. Wucknitz

    1. Argelander-Institut für Astronomie, Auf dem Hügel 71, D-53121 Bonn, Germany
    Search for more papers by this author

E-mail: mckean@astron.nl

ABSTRACT

The bright submillimetre (sub-mm) galaxy MM 18423+5938 at redshift 3.9296 has been predicted from mid-infrared (MIR) and millimetre photometry to have an exceptionally large total IR luminosity. We present new radio imaging at 1.4 GHz with the Westerbork Synthesis Radio Telescope that is used to determine a radio-derived total IR luminosity for MM 18423+5938 via the well-established radio–far-IR correlation. The flux density is found to be S1.4 GHz= 217 ± 37 μJy, which corresponds to a rest-frame luminosity density of L1.4 GHz= 2.32 ± 0.40 × 1025μ−1 W Hz−1, where μ is the magnification from a probable gravitational lens. The radio-derived total IR luminosity and star formation rate are L8−1000 μm= 5.6+4.1−2.4× 1013 μ−1  L and SFR =9.4+7.4−4.9× 103 μ−1 M yr−1, respectively, which are ∼9 times smaller than those previously reported. These differences are attributed to the IR spectral energy distribution of MM 18423+5938 being poorly constrained by the limited number of reliable photometric data that are currently available, and from a previous misidentification of the object at 70 μm. Using the radio derived total IR luminosity as a constraint, the temperature of the cold dust component is found to be Td∼ 24+7−5  K for a dust emissivity of β= 1.5 ± 0.5. The radio-derived properties of this galaxy are still large given the low excitation temperature implied by the CO emission lines and the temperature of the cold dust. Therefore, we conclude that MM 18423+5938 is probably gravitationally lensed.

Ancillary