2024MNRAS.533.2473C

We present Subaru/SCExAO + CHARIS broad-band (JHK) integral field spectroscopy of HD 34700 A in polarized light. CHARIS has the unique ability to obtain polarized integral field images at 22 wavelength channels in broad-band, as the incoming light is first split into different polarization states before passing though the lenslet array. We recover the transition disc around HD 34700 A in multiband polarized light in our data. We combine our polarized intensity data with previous total intensity data to examine the scattering profiles, scattering phase functions and polarized fraction of the disc at multiple wavelengths. We also carry out three-dimensional Monte Carlo radiative transfer simulations of the disc using MCFOST, and make qualitative comparisons between our models and data to constrain dust grain properties. We find that in addition to micron-sized dust grains, a population of submicron grains is needed to match the surface brightness in polarized light and polarized fraction. This could indicate the existence of a population of small grains in the disc, or it could be caused by Mie theory simulations using additional small grains to compensate for submicron structures of real dust aggregates. We find models that match the polarized fraction of the data but the models do not apply strong constraints on the dust grain type or compositions. We find no models that can match all observed properties of the disc. More detailed modelling using realistic dust aggregates with irregular surfaces and complex structures is required to further constrain the dust properties.