GG Tauri: the ring world

We present sub-arcsecond images of the mm dust emission and 13CO J=2–1 line emission in the young quadruple system GG Tau. These observations unambiguously resolve the circumbinary disk of the close (∼ 0.3′′) binary system into two distinct components: an extremely dense, sharp-edged ring, surrounded by an extended disk. Continuum emission is also detected from the center of this structure; it probably arises in the small circumstellar disk or disks of the binary. The kinematic data show that the ring+disk system is in Keplerian rotation and yield the estimate M = (1.28 ± 0.07)(D/140 pc)M for the mass of the binary stars. We derive the physical parameters of the ring and disk from these data and from new 2′′ resolution images of the HCO+ J=1–0 line and 3.4 mm continuum emission. The temperature in the ring + disk system is consistent with heating by the stellar light (including the IR excess coming from the inner disks). Comparison with the optical/NIR images indicates a disk thickness compatible with an hydrostatic equilibrium.