2019ApJ...872..179K

Analyzing multiband observations of dust continuum emission is one of the useful tools to constrain dust properties that help us to understand the physical properties of the protoplanetary disks. We perform a synthetic ALMA multiband analysis to find the best ALMA band set for constraining the dust properties of the TW Hya disk. We find that the Band [10, 6, 3] set is the best set among the possible combinations of ALMA Bands [3, 4, 5, 6, 7, 8, 9, 10]. We also find two conditions for the good ALMA band sets providing narrow constraint ranges on dust properties: (1) Band 9 or 10 is included in the band set, and (2) there are enough frequency intervals between the bands. These are related to the conditions that give good constraints on dust properties: the combination of optically thick and thin bands is required, and large β (β is the power-law index of dust opacity, κ_ν ∝ ν^β) and low dust temperature are preferable. To examine our synthetic analysis results, we apply the multiband analysis to ALMA archival data of the TW Hya disk at Bands 4, 6, 7, and 9. The Band [9, 6, 4] set provides the dust properties close to the model profile, while the Band [7, 6, 4] set gives the dust properties deviating from the model at all radii with too broad a constraint range to specify the accurate values of dust temperature, optical depth, and β. Since these features are expected by the synthetic multiband analysis, we confirm that the synthetic multiband analysis is consistent with the results derived from real data.