[M-IS03] アストロバイオロジー

[MIS03-02] Constraints on carbon isotope ratios in a planetary nursery: to understand the behavior of carbon

*Tomohiro Yoshida¹、Hideko Nomura¹、Takashi Tsukagoshi²、Kenji Furuya³、Seokho Lee⁴、Richard Teague⁵、Karin Öberg⁶ (1.NAOJ/SOKENDAI、2.Ashikaga University、3.NAOJ、4.KASI、5.MIT、6.CfA/Harvard)

キーワード：planet formation, exoplanet, protoplanetary disk, isotope, carbon, ALMA

To understand the origin of life ultimately, it is necessary to reveal the environment of planetary systems as a first steps. In this talk, we focus on the behavior of carbon. Carbon is a major element in the interstellar medium, and an ingredient of organic molecules. Meanwhile, planetary systems are formed in protoplanetary disks by coagulation of dust particles and capturing gas. To reveal the carbon behavior in disks, it is useful to use its isotope ratio, 12C/13C, in carbon-bearing molecules since the ratio may reflect the environments of the molecular formation. We present new analysis of 12CN/13CN in a protoplanetary disks around a classical T Tauri star, TW Hya, using the Atacama Large Millimeter / sub-millimeter Array (ALMA) archival data. The 12CN/13CN ratio is lower than the local interstellar value, and shows a potential radial variation. By comparing previous measurements of 12CO/13CO and H12CN/H13CN, it is suggested that the gas-phase in the disk is significantly carbon rich with respect to oxygen. This might be results of depletion of CO and other species during the disk evolution. The removed CO from gas would be incorporated to ice on dust grains, making more complex molecules including CO2 and organic molecules.