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Gas density perturbations induced by forming planet(s) in the AS 209 protoplanetary disk as seen with ALMA

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Authors : Cécile Favre, Davide Fedele, Luke Maud, Richard Booth, Marco Tazzari, Anna Miotello, Leonardo Testi, Dmitry Semenov & Simon Bruderer
Abstract : The formation of planets occurs within protoplanetary disks surrounding young stars, resulting in perturbation of the gas and dust surface densities. Here, we report the first evidence of spatially resolved gas surface density (Σgas) perturbation towards the AS 209 protoplanetary disk from the optically thin C18O (J=2−1) emission. The observations were carried out at 1.3mm with ALMA at a spatial resolution of about 0.3" × 0.2" (corresponding to 38 × 25 au). The C18O emission shows a compact (<60au), centrally peaked emission and an outer ring peaking at 140au, consistent with that observed in the continuum emission and, its azimuthally averaged radial intensity profile presents a deficit that is spatially coincident with the previously reported dust map. This deficit can only be reproduced with our physico-thermochemical disk model by lowering Σgas by nearly an order of magnitude in the dust gaps. Another salient result is that contrary to C18O, the DCO+ (J=3−2) emission peaks between the two dust gaps. We infer that the best scenario to explain our observations (C18O deficit and DCO+ enhancement) is a gas perturbation due to forming-planet(s), that is commensurate with previous continuum observations of the source along with hydrodynamical simulations. Our findings confirm that the previously observed dust gaps are very likely due to perturbation of the gas surface density that is induced by a planet of at least 0.2 M_Jupiter in formation. Finally, our observations also show the potential of using CO isotopologues to probe the presence of saturn mass planet(s).
Journal : Astrophysical Journal ArXiv