A likely planet-induced gap in the disk around T Cha
Nathanial P. Hendler, Paola Pinilla, Ilaria Pascucci, Adriana Pohl, Gijs Mulders, Thomas Henning, Ruobing Dong, Cathie Clarke, James Owen, David Hollenbach
(Submitted on 27 Nov 2017)
We present high resolution (0.11"×0.06") 3mm ALMA observations of the highly inclined transition disk around the star T Cha. Our continuum image reveals multiple dust structures: an inner disk, a spatially resolved dust gap, and an outer ring. When fitting sky-brightness models to the real component of the 3mm visibilities, we infer that the inner emission is compact (≤1au in radius), the gap width is between 18-28 au, and the emission from the outer ring peaks at ∼36 au. We compare our ALMA image with previously published 1.6μm VLT/SPHERE imagery. This comparison reveals that the location of the outer ring is wavelength dependent. More specifically, the peak emission of the 3mm ring is at a larger radial distance than that of the 1.6μm ring, suggesting that millimeter-sized grains in the outer disk are located further away from the central star than micron-sized grains. We discuss different scenarios to explain our findings, including dead zones, star-driven photoevaporation, and planet-disk interactions. We find that the most likely origin of the dust gap is from an embedded planet, and estimate --- for a single planet scenario --- that T Cha's gap is carved by a 1.2Mjup planet.