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摘要
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 similar to 9.4 kpc at an inclination angle of i = 54 degrees 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) x 10(11) M-circle dot. 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 x 10(10) K km s(-1) pc(2) and the inferred gas mass is M-H2 = 8.3 +/- 3.0 x 10(10) M-circle dot, which given the dynamical mass of the system is consistent with a CO-H-2 conversion factor of alpha= 5.5 +/- 2.0 M-circle dot (K km s(-1) pc(2))(-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) x (7.3/mu(IR)) M(circle dot)yr(-1), which demonstrates the composite star-forming and AGN nature of this system.
- 出版日期2018-5-28
