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arXiv · 1703.06661

Detection of submillimeter-wave [C I] emission in gaseous debris disks of 49 Ceti and Beta Pictoris

Aya E. Higuchi·Aki Sato·Takashi Tsukagoshi·Nami Sakai·Kazunari Iwasaki·Munetake Momose·Hiroshi Kobayashi·Daisuke Ishihara·Sakae Watanabe·Hidehiro Kaneda·Satoshi Yamamoto
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Abstract

We have detected [C I] 3P1-3P0 emissions in the gaseous debris disks of 49 Ceti and Beta Pictoris with the 10 m telescope of the Atacama Submillimeter Telescope Experiment, which is the first detection of such emissions. The line profiles of [C I] are found to resemble those of CO(J=3-2) observed with the same telescope and the Atacama Large Millimeter/submillimeter Array. This result suggests that atomic carbon (C) coexists with CO in the debris disks, and is likely formed by the photodissociation of CO. Assuming an optically thin [C I] emission with the excitation temperature ranging from 30 to 100 K, the column density of C is evaluated to be (2.2+-0.2)x10^17 and (2.5+-0.7)x10^16 cm^-2 for 49 Ceti and Beta Pictoris, respectively. The C/CO column density ratio is thus derived to be 54+-19 and 69+-42 for 49 Ceti and Beta Pictoris, respectively. These ratios are higher than those of molecular clouds and diffuse clouds by an order of magnitude. The unusually high ratios of C to CO are likely attributed to a lack of H2 molecules needed to reproduce CO molecules efficiently from C. This result implies a small number of H2 molecules in the gas disk; i.e., there is an appreciable contribution of secondary gas from dust grains.

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Aya E. Higuchi, Aki Sato, Takashi Tsukagoshi, Nami Sakai, Kazunari Iwasaki, Munetake Momose, Hiroshi Kobayashi, Daisuke Ishihara, Sakae Watanabe, Hidehiro Kaneda, Satoshi Yamamoto. 2017-03-20. Detection of submillimeter-wave [C I] emission in gaseous debris disks of 49 Ceti and Beta Pictoris. https://doi.org/10.3847/2041-8213%2Faa67f4

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