ALMA High-resolution Multiband Analysis for the Protoplanetary Disk around TW Hya

Abstract

We present a high-resolution (2.5 au) multiband analysis of the protoplanetary disk around TW Hya using ALMA long baseline data at Bands 3, 4, 6, and 7. We aim to reconstruct a high-sensitivity millimeter continuum image and revisit the spectral index distribution. The imaging is performed by combining new ALMA data at Bands 4 and 6 with available archive data. Two methods are employed to reconstruct the images; multi-frequency synthesis (MFS) and the fiducial image-oriented method, where each band is imaged separately and the frequency dependence is fitted pixel by pixel. We find that the MFS imaging with the second order of Taylor expansion can reproduce the frequency dependence of the continuum emission between Bands 3 and 7 in a manner consistent with previous studies and is a reasonable method to reconstruct the spectral index map. The image-oriented method provides a spectral index map consistent with the MFS imaging, but with a two times lower resolution. Mock observations of an intensity model were conducted to validate the images from the two methods. We find that the MFS imaging provides a high-resolution spectral index distribution with an uncertainty of $<10$~\%. Using the submillimeter spectrum reproduced from our MFS images, we directly calculated the optical depth, power-law index of the dust opacity coefficient ($\beta$), and dust temperature. The derived parameters are consistent with previous works, and the enhancement of $\beta$ within the intensity gaps is also confirmed, supporting a deficit of millimeter-sized grains within the gaps.

17pages, 12 figures, Accepted for publication in The Astrophysical Journal

References in corpus (14)

• Array Programming with NumPy
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Three radial gaps in the disk of TW Hydrae imaged with SPHERE
• Submillimeter emission associated with candidate protoplanets
• CO and dust properties in the TW Hya disk from high-resolution ALMA observations
• Mass inventory of the giant-planet formation zone in a solar nebula analog
• Discovery of a Disk Gap Candidate at 20 AU in TW Hydrae
• The anomalously low (sub)millimeter spectral indices of some protoplanetary disks may be explained by dust self-scattering
• Characterizing the dust content of disk substructures in TW Hya
• Chasing Shadows: Rotation of the Azimuthal Asymmetry in the TW Hya Disk
• Spiral Structure in the Gas Disk of TW Hya
• Dual-Wavelength ALMA Observations of Dust Rings in Protoplanetary Disks
• TW Hya: an old protoplanetary disc revived by its planet
• The Synthetic ALMA Multiband Analysis of the Dust Properties of the TW Hya Protoplanetary Disk