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

TL;DR

This study uses high-resolution interferometric observations to resolve the molecular gas disk in a gravitationally lensed quasar at z~2.8, revealing its structure, mass, and relation to typical high-redshift QSOs.

Contribution

First high-resolution CO(7-6) and continuum imaging of the host galaxy of RXJ0911.4+0551, providing detailed source modeling and insights into its molecular gas and dust properties.

Findings

Molecular disk radius of 1±0.2 kpc and inclination of 69±6°.

Low molecular gas mass and FIR luminosity consistent with a scaled-down high-z QSO.

Gas-to-dust ratio similar to that in a z=6.4 QSO, indicating comparable ISM properties.

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$\pm$0.2 kpc and an inclination of 69$\pm$6\deg, the continuum is more compact and is only marginally resolved by our observations. The relatively low molecular gas mass, $Mgas=(2.3\pm 0.5)\times 10^{9}$ Msolar, and far infrared luminosity, $LFIR=(7.2\pm 1.5) \times 10^{11}$ Lsolar, of this quasar could be explained by its relatively low dynamical mass, $Mdyn=(3.9\pm 0.9)\times 10^9$ Msolar. It would be a scaled-down version the 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 ($45\pm 17$) 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.