2009ApJ...702..318D

We detect the HD 32297 debris disk in scattered light at 1.6 and 2.05 µm. We use these new observations together with a previous scattered light image of the disk at 1.1 µm 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 ∼1".5 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 implies roughly 1 µm-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 interstellar medium cloud at a relative velocity of 15 km/s. We model the interaction of dust grains with H I 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.