Stumbling over planetary building blocks: AU Microscopii as an example of the challenge of retrieving debris-disk dust properties

Abstract

We explore whether assumptions about dust grain shape affect resulting estimates of the composition and grain size distribution of the AU Microscopii (AU Mic) debris disk from scattered light data collected by Lomax et al. (2018). The near edge-on orientation of the AU Mic debris disk makes it ideal for studying the effect of the scattering phase function (SPF) on the measured flux ratios as a function of wavelength and projected distance. Previous efforts to model the AU Mic debris disk have invoked a variety of dust grain compositions and explored the effect of porosity, but did not undertake a systematic effort to explore a full range of size distributions and compositions to understand possible degeneracies in fitting the data. The degree to which modelling dust grains with more realistic shapes compounds these degeneracies has also not previously been explored. We find differences in the grain properties retrieved depending on the grain shape model used. We also present here our calculations of porous grains of size parameters x = 0.1 to 48 and complex refractive indices (m = n+ik) ranging from n = 1.1 to 2.43 and k = 0 to 1.0, covering multiple compositions at visible and near infrared wavelengths such as ice, silicates, amorphous carbon, and tholins.

arXiv commentThis is a draft that I'd like to share before finalizing for journal submission. Feedback welcome

References in corpus (20)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Gaia Data Release 2. Summary of the contents and survey properties
• Scattering by Interstellar Dust Grains: Optical and Ultraviolet
• Scattering by Interstellar Dust Grains. II. X-Rays
• On the age of the $\beta$ Pictoris moving group
• Modeling optical properties of cosmic dust grains using a distribution of hollow spheres
• A planet within the debris disk around the pre-main-sequence star AU Microscopii
• Discovery of a large dust disk around the nearby star AU Microscopium
• Shaping the Kuiper belt size spectrum by shattering large but strengthless bodies
• The Signature of Primordial Grain Growth in the Polarized Light of the AU Mic Debris Disk
• STIS Coronagraphic Imaging of Fomalhaut: Main Belt Structure and the Orbit of Fomalhaut b
• Debris disk size distributions: steady state collisional evolution with P-R drag and other loss processes
• Where Are The M Dwarf Disks Older Than 10 Million Years?
• Near-infrared scattered light properties of the HR4796A dust ring: a measured scattering phase function from 13.6deg to 166.6deg
• A Sub-Millimeter Search of Nearby Young Stars for Cold Dust: Discovery of Debris Disks around Two Low-Mass Stars
• Azimuthal asymmetries in the debris disk around HD61005
• The AU Microscopii Debris Disk: Multiwavelength Imaging and Modeling
• Adaptive Optics Imaging of the AU Microscopii Circumstellar Disk: Evidence for Dynamical Evolution
• The AU Mic Debris Disk: far-infrared and submillimeter resolved imaging
• A SMACK Model of Colliding Planetesimals in the $\beta$ Pictoris Debris Disk

Cited by in corpus (4)

• Multiwavelength Vertical Structure in the AU Mic Debris Disk: Characterizing the Collisional Cascade
• A Multiband Study of the HR 4796A Disk in the Optical Using MagAO-X
• SCExAO/CHARIS Multi-Wavelength, High-Contrast Imaging of the BD+45${}^{\circ }$598 Debris Disk
• The Nearest, Brightest Debris Disk Host Stars: Updated Photosphere Models and Dust Properties for Stars with Saturated 2MASS Photometry