Young embedded protostars are fed from their surrounding envelopes through their protostellar disc. The physical structure of such early discs is still yet to be fully understood. We present ALMA and JVLA high-resolution (~6.5 - 12 au) continuum and polarization observations, followed by radiative transfer and synthetic observations of hydrodynamical simulations, to constrain the disk structure around one of the youngest Class 0 protostars, IRAS 16293-2422 B. Our results indicate that the young disc around IRAS 16293 B is hot (>400K) and sufficiently massive to undergo gravitational instabilities. The high disc mass (~ 0.3 Msun) results in very high optical depths at mm wavelengths. We study the effects of the maximum grain size in the disk by creating synthetic observations for the Stokes I and polarized emission for the case of polarization by dust self-scattering. Regardless of the maximum grain size, the predicted polarization fractions are too low to explain this young disk’s observed high (~ 2%) polarized emission.
Through this work, we have developed a new tool to automate the comparison between numerical simulations and observations called Synthesizer, including support for dust opacity mixing, polarization measurements, and full customization of the observing setup, which will be made publicly available.