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arXiv · 1605.00289

A Gap with a Deficit of Large Grains in the protoplanetary disk around TW Hya

Takashi Tsukagoshi·Hideko Nomura·Takayuki Muto·Ryohei Kawabe·Daiki Ishimoto·Kazuhiro D. Kanagawa·Satoshi Okuzumi·Shigeru Ida·Catherine Walsh·Tom J. Millar
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Abstract

We report $\sim$3 au resolution imaging observations of the protoplanetary disk around TW Hya at 145 and 233 GHz with the Atacama Large Millimeter/Submillimeter Array. Our observations revealed two deep gaps ($\sim$25--50 \%) at 22 and 37~au and shallower gaps (a few \%) at 6, 28, and 44~au, as recently reported by Andrews et al. (2016). The central hole with a radius of $\sim3$~au was also marginally resolved. The most remarkable finding is that the spectral index $\alpha (R)$ between bands 4 and 6 peaks at the 22~au gap. The derived power-law index of the dust opacity $\beta (R)$ is $\sim1.7$ at the 22~au gap and decreases toward the disk center to $\sim0$. The most prominent gap at 22~au could be caused by the gravitational interaction between the disk and an unseen planet with a mass of $\lesssim$1.5 $M_\mathrm{Neptune}$ although other origins may be possible. The planet-induced gap is supported by the fact that $\beta (R)$ is enhanced at the 22~au gap, indicating a deficit of $\sim$mm-sized grains within the gap due to dust filtration by a planet.

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Takashi Tsukagoshi, Hideko Nomura, Takayuki Muto, Ryohei Kawabe, Daiki Ishimoto, Kazuhiro D. Kanagawa, Satoshi Okuzumi, Shigeru Ida, Catherine Walsh, Tom J. Millar. 2016-05-01. A Gap with a Deficit of Large Grains in the protoplanetary disk around TW Hya. https://doi.org/10.3847/2041-8205%2F829%2F2%2Fl35

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