Mapping CO Gas in the GG Tauri A Triple System with 50 AU Spatial
  Resolution
  We aim to unveil the observational imprint of physical mechanisms that govern
planetary formation in the young, multiple system GG Tau A. We present ALMA
observations of $^{12}$CO and $^{13}$CO 3-2 and 0.9 mm continuum emission with
0.35" resolution. The $^{12}$CO 3-2 emission, found within the cavity of the
circumternary dust ring (at radius $< 180$ AU) where no $^{13}$CO emission is
detected, confirms the presence of CO gas near the circumstellar disk of GG Tau
Aa. The outer disk and the recently detected hot spot lying at the outer edge
of the dust ring are mapped both in $^{12}$CO and $^{13}$CO. The gas emission
in the outer disk can be radially decomposed as a series of slightly
overlapping Gaussian rings, suggesting the presence of unresolved gaps or dips.
The dip closest to the disk center lies at a radius very close to the hot spot
location at $\sim250-260$~AU. The CO excitation conditions indicate that the
outer disk remains in the shadow of the ring. The hot spot probably results
from local heating processes. The two latter points reinforce the hypothesis
that the hot spot is created by an embedded proto-planet shepherding the outer
disk.
