[P-CG24] アルマによる惑星科学の新展開

[PCG24-P02] Investigating the gas-to-dust ratio in the protoplanetary disk of HD 142527

*Soon Kang-Lou¹、百瀬 宗武¹、武藤 恭之²、塚越 崇³、片岡 章雅³、花輪 知幸⁴、深川 美里³、西合 一矢³、芝井 広⁵ (1.茨城大学、2.工学院大学、3.国立天文台、4.千葉大学、5.大阪大学)

キーワード：HD 142527、原始惑星系円盤、ガス・ダスト比

We present the ALMA observations of the 98.5 GHz dust continuum and the ¹³CO J = 1 – 0 and C¹⁸O J = 1 – 0 line emission towards the protoplanetary disk of HD 142527. The 98.5 GHz continuum shows a strong azimuthal-asymmetric distribution similar to the previously reported 336 GHz continuum, and its peak emission at the dust concentrated northern region is optically thin at approximately 8 K. In every position angle, the peak brightness temperature of C¹⁸O J = 1 – 0 emission (≦ 25 K) is lower than that of the optically thick ¹³CO J = 3 – 2 (≈ 36 K), indicating that the C¹⁸O is optically thin. We derive the gas and dust surface densities, Σ_g and Σ_d, of the disk of HD 142527 by using the ALMA Band 3 and Band 7 observations. In the analyses we assume the local thermodynamic equilibrium and the disk temperature to be the same as the peak brightness temperature of ¹³CO J = 3 – 2 with continuum emission. We successfully derived the gas-to-dust ratio G/D, defined as Σ_g/Σ_d, distribution across the disk. The ratio varies azimuthally, where it is ∼3 and ∼20 in the disk northern and southern regions, respectively. We also found that Σ_g varies approximately as ∝ Σ_d^0.5, or equivalently G/D ∝ Σ_d^-0.5. In addition, our results show that the peak Σ_d is located ahead of the peak Σ_g; if the latter correspond to a vortex of high gas pressure, the results indicate that the dust are trapped ahead of the vortex, which is predicted by theoretical studies.