Resolving the molecular gas around the lensed quasar RXJ0911.4+0551^⋆

¹ Université de Toulouse, UPS-OMP, IRAP, 31400 Toulouse, France
e-mail: frederic.boone@irap.omp.eu
² CNRS, IRAP, 9 Av. colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
³ VATLY, INST, 179 Hoang Quoc Viet, Cau Giay, Hanoi, Vietnam
⁴ Institute of Physics, 10 Dao Tan, Hanoi, Vietnam
⁵ Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
⁶ Laboratoire d’Astrophysique de Marseille, CNRS-Université Aix-Marseille, 13388 Marseille Cedex, France
⁷ Institut d’Astrophysique Spatiale, Bât. 121, Université Paris-Sud, 91405 Orsay Cedex, France
⁸ LERMA, Observatoire de Paris, UMR 8112 du CNRS, 75014 Paris, France

Received: 26 February 2013
Accepted: 20 March 2013

Abstract

We report on high angular resolution observations of the CO(7–6) line and millimeter continuum in the host galaxy of the gravitationally lensed (z ~ 2.8) quasar RXJ0911.4+0551 using the Plateau de Bure Interferometer. Our CO observations resolve the molecular disk of the source. Using a lens model based on HST observations, we fit source models to the observed visibilities. We estimate a molecular disk radius of 1 ± 0.2 kpc and an inclination of 69 ± 6 deg, the continuum is more compact and is only marginally resolved by our observations. The relatively low molecular gas mass, M_gas = (2.3 ± 0.5) × 10⁹ M_⊙, and far-infrared (FIR) luminosity, L_FIR = (7.2 ± 1.5) × 10¹¹ L_⊙, of this quasar could be explained by its relatively low dynamical mass, M_dyn = (3.9 ± 0.9) × 10⁹ M_⊙. It would be a scaled-down version the quasi-stellar objects (QSOs) usually found at high-z. The FIR and CO luminosities lie on the correlation found for QSOs from low to high redshifts and the gas-to-dust ratio (45 ± 17) is similar to the one measured in the z = 6.4 QSO, SDSS J1148+5251. Differential magnification affects the continuum-to-line luminosity ratio, the line profile, and possibly the spectral energy distribution.