Poster Presentation
High-resolution multiband imaging for the radial variation of the spectral index in the protoplanetary disk around TWHya
Presenter: Takashi Tsukagoshi (National Astronomical Observatory of Japan)
We present high-resolution (2.5au) multiband analysis of the protoplanetary disk around TW Hya with ALMA. In our previous study (Tsukagoshi et al. 2016), we found a trend that the spectral index decreases toward the disk center from 2.8 to 1.8 with enhancement at the inner gap at 25au. However, the spectral index map was taken during the array configuration that was not optimized, and the uncertainty still remains in the distribution of the spectral index.
To obtain a reliable spectral index map, we used ALMA archive data at Band 4, 6, and 7 to reconstruct the combined intensity at 244GHz and the spectral index maps. The sensitivity was achieved to be 8.6uJy/beam, which is approximately three times better than that of our previous study. The spectral index decreases toward the disk center from 2.8 to 1.8, as previously reported. We also find that there is a variation of the spectral index associated with the inner gap at 25au, but the peak value is slightly updated to be 2.5. The lower spectral index than 2 at the inner part of the disk could be interpreted by taking scattering into account. We also found in the intensity map that there is a tail-like feature that azimuthally extends for ~0.5arcsec (~30au) from the millimeter blob at 52au reported by Tsukagoshi et al. (2019).