Spiral Structure and Differential Dust Size Distribution in the LKHα 330 Disk

Eiji Akiyama , Jun Hashimoto , Hauyu Baobab Liu , Jennifer I-Hsiu Li , Michael Bonnefoy (1) , Ruobing Dong , Yasuhiro Hasegawa , Thomas Henning , Michael L. Sitko , Markus Janson , Markus Feldt , John Wisniewski , Tomoyuki Kudo , Nobuhiko Kusakabe , Takashi Tsukagoshi , Munetake Momose , Takayuki Muto , Tetsuo Taki , Masayuki Kuzuhara , Mayama Satoshi , Michihiro Takami , Nagayoshi Ohashi , Carol A. Grady , Jungmi Kwon , Christian Thalmann , Lyu Abe , Wolfgang Brandner , Timothy D. Brandt , Joseph C. Carson , Sebastian Egner , Miwa Goto , Olivier Guyon , Yutaka Hayano , Masahiko Hayashi , Saeko S. Hayashi , Klaus W. Hodapp , Miki Ishii , Masanori Iye , Gillian R. Knapp , Ryo Kandori , Taro Matsuo , Michael W. Mcelwain , Shoken Miyama , Jun-Ichi Morino , Amaya Moro-Martin , Tetsuo Nishimura , Tae-Soo Pyo , Eugene Serabyn , Takuya Suenaga , Hiroshi Suto , Ryuji Suzuki , Yasuhiro H. Takahashi , Naruhisa Takato , Hiroshi Terada , Daigo Tomono , Edwin L. Turner , Makoto Watanabe , Toru Yamada , Hideki Takami , Tomonori Usuda , Motohide Tamura

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

Dust trapping accelerates the coagulation of dust particles, and, thus, it represents an initial step toward the formation of planetesimals. We report H-band (1.6 μm) linear polarimetric observations and 0.87 mm interferometric continuum observations toward a transitional disk around LkHα 330. As a result, a pair of spiral arms were detected in the H-band emission, and an asymmetric (potentially arm-like) structure was detected in the 0.87 mm continuum emission. We discuss the origin of the spiral arm and the asymmetric structure and suggest that a massive unseen planet is the most plausible explanation. The possibility of dust trapping and grain growth causing the asymmetric structure was also investigated through the opacity index (β) by plotting the observed spectral energy distribution slope between 0.87 mm from our Submillimeter Array observation and 1.3 mm from literature. The results imply that grains are indistinguishable from interstellar medium-like dust in the east side (β =2.0+/- 0.5) but are much smaller in the west side β ={0.7}_-0.4^+0.5, indicating differential dust size distribution between the two sides of the disk. Combining the results of near-infrared and submillimeter observations, we conjecture that the spiral arms exist at the upper surface and an asymmetric structure resides in the disk interior. Future observations at centimeter wavelengths and differential polarization imaging in other bands (Y-K) with extreme AO imagers are required to understand how large dust grains form and to further explore the dust distribution in the disk.

Keywords: planetary systems; stars: pre-main sequence; stars: individual: LkHα 330; techniques: interferometric; Astrophysics - Earth and Planetary Astrophysics

Domains: Sciences of the Universe [physics]

Eiji Akiyama, Jun Hashimoto, Hauyu Baobab Liu, Jennifer I-Hsiu Li, Michael Bonnefoy, et al.. Spiral Structure and Differential Dust Size Distribution in the LKHα 330 Disk. The Astronomical Journal, 2016, 152, ⟨10.3847/1538-3881/152/6/222⟩. ⟨insu-03691473⟩