SIMBAD references

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/140pc)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 3.4mm 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.