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

Domenii publicaţii > Fizica + Tipuri publicaţii > Articol în revistã ştiinţificã

Autori: J. P. McKean, A. Berciano Alba, F. Volino, V. Tudose, M. A. Garrett, A. F. Loenen, Z. Paragi, O. Wucknitz

Editorial: Monthly Notices of the Royal Astronomical Society, 414, p.L11, 2011.


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 S(1.4 GHz)= 217 +/- 37 microJy, which corresponds to a rest-frame luminosity density of L (1.4 GHz)= 2.32 +/- 0.40 x 10^{25} mu^{-1} W Hz^{-1}, where mu is the magnification from a probable gravitational lens. The radio-derived total IR luminosity and star formation rate are L (8-1000 microm)= 5.6 (+4.1; -2.4) x 10^{13} mu^{-1} L_Sun; and SFR =9.4 (+7.4; -4.9) x 10^{3} mu^{-1} M_Sun 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 microm. Using the radio derived total IR luminosity as a constraint, the temperature of the cold dust component is found to be T_d~ 24 (+7; -5) K for a dust emissivity of beta= 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.

Cuvinte cheie: strong gravitational lensing, high-redshift galaxies, starburst galaxies