Oxford University Press (OUP), Publications of Astronomical Society of Japan, 2019
DOI: 10.1093/pasj/psz112
Full text: Unavailable
Abstract We present ALMA observations of the 98.5 GHz dust continuum and the ${}^{13}\mbox{CO}J = 1$–0 and $\mbox{C}^{18}\mbox{O}J = 1$–0 line emissions of the protoplanetary disk associated with HD 142527. The 98.5 GHz continuum shows a strong azimuthal-asymmetric distribution similar to that of the previously reported 336 GHz continuum, with a peak emission in dust concentrated region in the north. The disk is optically thin in both the 98.5 GHz dust continuum and the $\mbox{C}^{18}\mbox{O}J = 1$–0 emissions. We derive the distributions of gas and dust surface densities, $Σ _\mathrm{g}$ and $Σ _\mathrm{d}$, and the dust spectral opacity index, $β$, in the disk from ALMA Band 3 and Band 7 data. In the analyses, we assume the local thermodynamic equilibrium and the disk temperature to be equal to the peak brightness temperature of ${}^{13}\mbox{CO}\,J = 3$–2 with a continuum emission. The gas-to-dust ratio, $\mathrm{G/D}$, varies azimuthally with a relation $\mathrm{G/D} ∝ Σ _\mathrm{d}^{-0.53}$, and $β$ is derived to be $≈ 1$ and $≈ 1.7$ in the northern and southern regions of the disk, respectively. These results are consistent with the accumulation of larger dust grains in a higher pressure region. In addition, our results show that the peak $Σ _\mathrm{d}$ is located ahead of the peak $Σ _\mathrm{g}$. If the latter corresponds to a vortex of high gas pressure, the results indicate that the dust is trapped ahead of the vortex, as predicted by some theoretical studies.