Multiband polarimetric imaging of HD 34700 with SCExAO/CHARIS

TL;DR

This study uses advanced polarimetric imaging with SCExAO/CHARIS to analyze the HD 34700 A disk, revealing the presence of small dust grains and highlighting the need for more complex models to fully understand dust properties.

Contribution

First broadband polarized integral field spectroscopy of HD 34700 A with SCExAO/CHARIS, combining observations and radiative transfer modeling to study dust grain properties.

Findings

Detection of micron-sized and sub-micron dust grains in the disk.

Models match polarized fraction but not all observed properties.

Small grains may indicate complex dust structures or compositions.

Abstract

We present Subaru/SCExAO + CHARIS broadband (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 broadband, as the incoming light is first split into different polarization states before passing though the lenslet array. We recover the transition disk 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 disk at multiple wavelengths. We also carry out 3D Monte Carlo radiative transfer simulations of the disk 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 sub-micron 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 disk, or it could be caused by Mie theory simulations using additional small grains to compensate for sub-micron 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 disk. More detailed modeling using realistic dust aggregates with irregular surfaces and complex structures is required to further constrain the dust properties.