The Sizes and Depletions of the Dust and Gas Cavities in the Transitional Disk J160421.7-213028
Dong, Ruobing; Ohashi, Nagayoshi; Tamura, Motohide; Takami, Michihiro; Wisniewski, John; Liu, Hauyu Baobab; Tsukagoshi, Takashi; Hashimoto, Jun; Kudo, Tomoyuki; Muto, Takayuki; Zhu, Zhaohuan; Yang, Yi; Akiyama, Eiji; Knapp, Gillian R.; Chiang, Eugene; van der Marel, Nienke; Bruderer, Simon; Brown, Joanna; Koyamatsu, Shin; Rich, Evan; Satoshi, Mayama
United States, Japan, Germany, Taiwan
Abstract
We report ALMA Cycle 2 observations of 230 GHz (1.3 mm) dust continuum emission, and 12CO, 13CO, and C18O J = 2-1 line emission, from the Upper Scorpius transitional disk [PZ99] J160421.7-213028, with an angular resolution of ∼0\buildrel{\prime\prime}\over{.} 25 (35 au). Armed with these data and existing H-band scattered light observations, we measure the size and depth of the disk’s central cavity, and the sharpness of its outer edge, in three components: sub-μm-sized “small” dust traced by scattered light, millimeter-sized “big” dust traced by the millimeter continuum, and gas traced by line emission. Both dust populations feature a cavity of radius ∼70 au that is depleted by factors of at least 1000 relative to the dust density just outside. The millimeter continuum data are well explained by a cavity with a sharp edge. Scattered light observations can be fitted with a cavity in small dust that has either a sharp edge at 60 au, or an edge that transitions smoothly over an annular width of 10 au near 60 au. In gas, the data are consistent with a cavity that is smaller, about 15 au in radius, and whose surface density at 15 au is {10}3+/- 1 times smaller than the surface density at 70 au; the gas density grades smoothly between these two radii. The CO isotopologue observations rule out a sharp drop in gas surface density at 30 au or a double-drop model, as found by previous modeling. Future observations are needed to assess the nature of these gas and dust cavities (e.g., whether they are opened by multiple as-yet-unseen planets or photoevaporation).