# ALMA Detection of Extended Millimeter Halos in the HD 32297 and HD 61005 Debris Disks

## TL;DR

This study uses ALMA observations to reveal extended millimeter-sized grain halos in the debris disks of HD 32297 and HD 61005, providing new insights into their structure and composition.

## Contribution

First high-resolution ALMA images of these debris disks at millimeter wavelengths, showing extended halos of large grains and gas, with detailed modeling of their structure.

## Key findings

- Disks have a two-component structure with a planetesimal belt and an extended halo.
- Halos extend to hundreds of AU, containing millimeter-sized grains.
- Detection of CO gas co-located with dust in HD 32297.

## Abstract

We present ALMA 1.3 mm (230 GHz) observations of the HD 32297 and HD 61005 debris disks, two of the most iconic debris disks due to their dramatic swept-back wings seen in scattered light images. These observations achieve sensitivities of 14 and 13 $\mu$Jy beam$^{-1}$ for HD 32297 and HD 61005, respectively, and provide the highest resolution images of these two systems at millimeter wavelengths to date. By adopting a MCMC modeling approach, we determine that both disks are best described by a two-component model consisting of a broad ($\Delta R/R> 0.4$) planetesimal belt with a rising surface density gradient, and a steeply falling outer halo aligned with the scattered light disk. The inner and outer edges of the planetesimal belt are located at $78.5\pm8.1$ AU and $122\pm3$ AU for HD 32297, and $41.9\pm0.9$ AU and $67.0\pm0.5$ AU for HD 61005. The halos extend to $440\pm32$ AU and $188\pm8$ AU, respectively. We also detect $^{12}$CO J$=2-1$ gas emission from HD 32297 co-located with the dust continuum. These new ALMA images provide observational evidence that larger, millimeter-sized grains may also populate the extended halos of these two disks previously thought to only be composed of small, micron-sized grains. We discuss the implications of these results for potential shaping and sculpting mechanisms of asymmetric debris disks.