Interstellar Medium Sculpting of the HD 32297 Disk

TL;DR

This study analyzes the HD 32297 debris disk's structure and scattering properties across multiple wavelengths, revealing asymmetries likely caused by interaction with a dense interstellar medium cloud.

Contribution

It provides new multi-wavelength observations and models the disk's morphology as influenced by interstellar medium interaction, a novel explanation for observed asymmetries.

Findings

Detection of the disk at 1.6 and 2.05 microns.

Identification of asymmetries in color and morphology.

Proposed ISM interaction as the cause of asymmetries.

Abstract

We detect the HD 32297 debris disk in scattered light at 1.6 and 2.05 \micron. We use these new observations together with a previous scattered light image of the disk at 1.1 \micron to examine the structure and scattering efficiency of the disk as a function of wavelength. In addition to surface brightness asymmetries and a warped morphology beyond $\sim$1\farcs5 for one lobe of the disk, we find that there exists an asymmetry in the spectral features of the grains between the northeastern and southwestern lobes. The mostly neutral color of the disk lobes imply roughly 1 \micron-sized grains are responsible for the scattering. We find that the asymmetries in color and morphology can plausibly be explained by HD 32297's motion into a dense ISM cloud at a relative velocity of 15 km s$^{-1}$. We model the interaction of dust grains with HI gas in the cloud. We argue that supersonic ballistic drag can explain the morphology of the debris disks of HD 32297, HD 15115, and HD 61005.