Detection of CO (2–1) and Radio Continuum Emission from the [CLC][ITAL]z[/ITAL][/CLC] = 4.4 QSO BRI 1335−0417

Abstract

We have detected redshifted CO (2-1) emission at 43 GHz and radio continuum emission at 1.47 and 4.86 GHz from the z = 4.4 QSO BRI 1335-0417 using the Very Large Array. The CO data imply optically thick emission from warm (>30 K) molecular gas with a total mass, M(H2), of (1.5 ± 0.3) × 1011 M☉, using the standard Galactic gas mass-to-CO luminosity conversion factor. We set an upper limit to the CO source size of 11 and a lower limit of 023(Tex/50 K)-1/2, where Tex is the gas excitation temperature. We derive an upper limit to the dynamical mass of 2 × 1010sin−2 i M☉, where i is the disk inclination angle. Reconciling the gas mass with the dynamical mass requires either a nearly face-on disk (i < 25°) or a gas mass-to-CO luminosity conversion factor significantly lower than the Galactic value. The spectral energy distribution from the radio to the rest-frame infrared of BRI 1335-0417 is consistent with that expected from a nuclear starburst galaxy, with an implied massive star formation rate of 2300 ± 600 M☉ yr-1.