* Astronomy

Title: Polarimetric Imaging of Large Cavity Structures in the Pre-transitional Protoplanetary Disk around PDS 70: Observations of the disk
Authors: Jun Hashimoto, Ruobing Dong, Tomoyuki Kudo, M. Honda, M. McClure, Z. Zhu, T. Muto, John Wisniewski, Lyu Abe, Wolfgang Brandner, Timothy Brandt, J. Carson, Sebastian Egner, Markus Feldt, Misato Fukagawa, Miwa Goto, Carol Anne Grady, Olivier Guyon, Yutaka Hayano, Masao Hayashi, Saeko Hayashi, Thomas Henning, Klaus Hodapp, Miki Ishii, Masanori Iye, Markus Janson, Ryo Kandori, Gillian Knapp, Nobuhiko Kusakabe, Masayuki Kuzuhara, Jungmi Kwon, Taro Matsuo, Satoshi Mayama, Michael McElwain, Shoken Miyama, Jun-Ichi Morino, Amaya Moro-Martin, T. Nishimura, Tae-Soo Pyo, G. Serabyn, Takuya Suenaga, Hiroshi Suto, Ryuji Suzuki, Y. H. Takahashi, Michihiro Takami, Naruhisa Takato, Hiroshi Terada, Christian Thalmann, Daigo Tomono, Edwin L. Turner, Makoto Watanabe, Toru Yamada, Hideki Takami, Tomonori Usuda, et al. (1 additional author not shown)

We present high resolution H-band polarised intensity (PI; FWHM = 0.1": 14 AU) and L'-band imaging data (FWHM = 0.11": 15 AU) of the circumstellar disk around the weak-lined T Tauri star PDS 70 in Centaurus at a radial distance of 28 AU (0.2") up to 210 AU (1.5"). In both images, a giant inner gap is clearly resolved for the first time, and the radius of the gap is ~70 AU. Our data show that the geometric center of the disk shifts by ~6 AU toward the minor axis. We confirm that the brown dwarf companion candidate to the north of PDS 70 is a background star based on its proper motion. As a result of SED fitting by Monte Carlo radiative transfer modelling, we infer the existence of an optically thick inner disk at a few AU. Combining our observations and modelling, we classify the disk of PDS 70 as a pre-transitional disk. Furthermore, based on the analysis of L'-band imaging data, we put an upper limit mass of companions at ~30 to ~50MJ within the gap. Taking account of the presence of the large and sharp gap, we suggest that the gap could be formed by dynamical interactions of sub-stellar companions or multiple unseen giant planets in the gap.

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