Testing the vortex hypothesis in a protoplanetary disk

The HD34282 is a protoplanetary disk that hosts an azimuthal asymmetry in the mm dust continuum observed by ALMA. The asymmetry coincides with a one-arm spiral and shadow on the outer disk in near-infrared scattered light, which is coherent with signatures of a vortex shown in simulations. HD34282 thus one of few disks with solid evidence for the presence of a vortex in both NIR and mm observations. The presence of vortices is key to planet formation since they are prime sites to form planetesimals and the potential birthplace of the planets. In our work, we aim to further test the vortex hypothesis for HD34282 by examining two additional theoretical predictions for vortices: i) smaller dust traced at shorter wavelengths is less concentrated azimuthally than larger dust traced at longer wavelengths; ii) dust at the vortex center can reach a maximum dust size of several mm, one order of magnitude or larger than that in the background rings. This is done by carrying out high-resolution multi-wavelength dust continuum observations. We will compare the azimuthal extent of the structure at multiple wavelengths and constrain the dust properties via multi-wavelength spectral energy distribution modelling. Once two predictions are verified, this project will have the potential to provide the most definitive verification of a vortex in a protoplanetary disk and associate the azimuthal asymmetries mm continuum observation with vortices. On the other hand, the negative result would challenge the current theory and motivate alternative explanations for both azimuthal asymmetries in the mm continuum and one-arm spirals in NIR.