# Dust Polarization in Four Protoplanetary Disks at 3 mm: Further Evidence of Multiple Origins

## TL;DR

This study presents ALMA polarimetric observations of four protoplanetary disks at 3 mm, revealing two polarization patterns that suggest different dust grain alignment mechanisms and potential size variations across disks.

## Contribution

It provides the first detailed comparison of polarization morphologies in multiple disks at 3 mm, highlighting evidence for multiple dust polarization origins.

## Key findings

- DG Tau and Haro 6-13 show polarization consistent with radiation alignment.
- RY Tau and MWC 480 exhibit polarization indicative of self-scattering.
- Variation in polarization suggests differences in dust grain sizes among disks.

## Abstract

We present polarimetric observations of four Class II protoplanetary disks (DG Tau, Haro 6-13, RY Tau, and MWC 480) taken with the Atacama Large Millimeter/submillimeter Array (ALMA) at 3 mm. The polarization morphologies observed fall into two distinct categories: azimuthal polarization (DG Tau and Haro 6-13) and polarization parallel to the disk minor axis (RY Tau and MWC 480). The mechanisms responsible for disk polarization at millimeter and submillimeter wavelengths are currently under debate. In this Letter, we investigate two mechanisms capable of producing polarized dust emission in disks: self-scattering and grain alignment to the radiation anisotropy. The polarization morphologies of DG Tau and Haro 6-13 are broadly consistent with that expected from radiation alignment (though radiative alignment still does not account for all of the features seen in these disks), while RY Tau and MWC 480 are more consistent with self-scattering. Such a variation in the polarized morphology may provide evidence of dust grain size differences between the sources.