We report 3 au resolution imaging observations of the protoplanetary disk aroundTW Hya at 145 and 233 GHz with the Atacama Large Millimeter/Submillimeter Array.Our observations revealed two deep gaps (~25-50 %) at 22 and 37 au and shallowergaps (a few %) at 6, 28, and 44 au, as recently reported by Andrews et al. (2016). Thecentral hole with a radius of 3 au was also marginally resolved. The most remarkablefinding is that the spectral index α(R) between bands 4 and 6 peaks at the 22 au gap.The derived power-law index of the dust opacity β(R) is ~1.7 at the 22 au gap anddecreases toward the disk center to ~0. The most prominent gap at 22 au could becaused by the gravitational interaction between the disk and an unseen planet with amass of ≲1.5 MNeptune although other origins may be possible. The planet-induced gap is supported by the fact that β(R) is enhanced at the 22 au gap, indicating a deficitof mm-sized grains within the gap due to dust filtration by a planet.
Tsukagoshi, T., Nomura, H., Muto, T., Kawabe, R., Ishimoto, D., Kanagawa, K. D., Okuzumi, S., Ida, S., Walsh, C., & Millar, T. J. (2016). A Gap with a Deficit of Large Grains in the Protoplanetary Disk around TW Hya. Astrophysical Journal Letters, 829(2), [L35]. https://doi.org/doi:10.3847/2041-8205/829/2/L35