Direct Imaging of the HD 35841 Debris Disk: A Polarized Dust Ring from Gemini Planet Imager and an Outer Halo from /STIS

Abstract

We present new high resolution imaging of a light-scattering dust ring and halo around the young star HD 35841. Using spectroscopic and polarimetric data from the Gemini Planet Imager in H-band (1.6 mu m), we detect the highly inclined (i = 85 degrees) ring of debris down to a projected separation of similar to 12 au (similar to 0.'' 12) for the first time. Optical imaging from HST/STIS shows a smooth dust halo extending outward from the ring to >140 au (>1.'' 1 4). We measure the ring's scattering phase function and polarization fraction over scattering angles of 22 degrees-125 degrees, showing a preference for forward scattering and a polarization fraction that peaks at similar to 30% near the ansae. Modeling of the scattered-light disk indicates that the ring spans radii of similar to 60-220 au, has a vertical thickness similar to that of other resolved dust rings, and contains grains as small as 1.5 mu m in diameter. These models also suggest the grains have a low porosity, are more likely to consist of carbon than astrosilicates, and contain significant water ice. The halo has a surface brightness profile consistent with that expected from grains pushed by radiation pressure from the main ring onto highly eccentric but still bound orbits. We also briefly investigate arrangements of a possible inner disk component implied by our spectral energy distribution models, and speculate about the limitations of Mie theory for doing detailed analyses of debris disk dust populations.