CO Gas orbiting around the GG Tauri A triple System: rings beyond the ring ?
Tang et al
We aim at unveiling the observational imprint of physical mechanisms that govern planetary formation in the young, multiple system GG Tau A. We present ALMA observations of 12CO and 13CO 3-2 and continuum at 0.9 mm at 0.35" resolution. The 12CO gas, found in the cavity of the dust ring where no 13CO gas is detected, confirms the existence of a CO accretion shock near the circumstellar disk of GG Tau Aa. The outer disk and the hot spot lying at the outer edge of the dust ring are observed both in 12CO and 13CO. The gas emission in the outer disk can be radially decomposed in a series of slightly overlapping gaussian rings, suggesting the presence of unresolved gaps. The dip closest to the disk center lies at a radius very close to the CO hot spot location (∼250−260~au). Studies of the CO excitation conditions reveal that the outer disk remains in the shadow of the ring. The hot spot probably results from local heating processes. The two latter points strongly support the hypothesis making the hot spot an embedded proto-planet shepherding the outer disk and accreting surrounding material which may be traced by the the redshifted component observed in the spectra around the hot spot.