[P-PS04] [EJ] New developments of planetary sciences with ALMA

[PPS04-P09] Detection of submillimeter-wave [C I] emission in gaseous debris disks; 49 Ceti and β Pictoris

*Aya Higuchi¹, Sato Aki², Takashi Tsukagoshi², Nami Sakai¹, Munetake Momose², Hiroshi Kobayashi³, Daisuke Ishihara³, Sakae Watanabe³, Hidehiro Kaneda³, Kazunari Iwasaki⁴, Satoshi Yamamoto⁵ (1.RIKEN, 2.Ibaraki University, 3.Nagoya University, 4.Doshisha University, 5.The University of Tokyo)

Keywords:debris disk

We have detected the [C I]³P₁–³P₀ emission in the gaseous debris disks, 49 Ceti and β Pictoris, with the Atacama Submillimeter Telescope Experiment (ASTE). The line profiles of [C I] is found to be those of CO(J=3–2) observed with the same telescope as well as the Atacama Large Millimeter/submillimeter Array (ALMA). This result suggests that the atomic carbon (C) coexists with CO in the debris disks, and is likely formed by photodissociation of CO. The C/CO column density ratio is thus derived to be 54±19 to 69±42 for 49 Ceti and β Pictoris, respectively. These ratios are higher than those of protoplanetary disks, molecular clouds, and diffuse clouds by an order of magnitude. From the result, we suggest that the origin of a large amount of [C I] in the debris disk would likely be a small amount of the H₂ molecule in the gas disk. This implies a significant contribution of the secondary gas coming out from dust grains.