Multiwavelength Vertical Structure in the AU Mic Debris Disk: Characterizing the Collisional Cascade

Abstract

Debris disks are scaled-up analogs of the Kuiper Belt in which dust is generated by collisions between planetesimals. In the "collisional cascade" model of debris disks, dust lost to radiation pressure and winds is constantly replenished by grinding collisions between planetesimals. The model assumes that collisions are destructive and involve large velocities; this assumption has not been tested beyond our Solar System. We present 0"25 ($\approx$2.4 au) resolution observations of the $\lambda$ = 450 $\mu$m dust continuum emission from the debris disk around the nearby M dwarf AU Microscopii with the Atacama Large Millimeter/submillimeter Array. We use parametric models to describe the disk structure, and an MCMC algorithm to explore the posterior distributions of the model parameters; we fit the structure of the disk to both our data and archival $\lambda =1.3$ mm data (Daley et al. 2019), from which we obtain two aspect ratio measurements at 1.3 mm ($h_{1300}$ = 0.025${}_{-0.002}^{+0.008}$) and at 450 $\mu$m ($h_{450}$ = 0.019${}_{-0.001}^{+0.006}$), as well as the grain size distribution index $q=$ 3.03 $\pm$ 0.02. Contextualizing our aspect ratio measurements within the modeling framework laid out in Pan & Schlichting (2012), we derive a power law index of velocity dispersion as a function of grain size $p=0.28\pm 0.06$ for the AU Mic debris disk. This result implies that smaller bodies are more easily disrupted than larger bodies by collisions, which is inconsistent with the strength regime usually assumed for such small bodies. Possible explanations for this discrepancy are discussed.

17 pages, 6 figures, 3 tables. Accepted for publication in ApJ

References in corpus (29)

• Array Programming with NumPy
• On the age of the $\beta$ Pictoris moving group
• Transience of hot dust around sun-like stars
• Spitzer IRS Spectroscopy of IRAS-Discovered Debris Disks
• A Three-Dimensional View of Turbulence: Constraints on Turbulent Motions in the HD 163296 Protoplanetary Disk using DCO${}^{+}$
• A planet within the debris disk around the pre-main-sequence star AU Microscopii
• Probing for Exoplanets Hiding in Dusty Debris Disks: Disk Imaging, Characterization, and Exploration with HST/STIS Multi-Roll Coronagraphy
• Long-Term Collisional Evolution of Debris Disks
• Steady-State Size Distributions for Collisional Populations: Analytical Solution with Size-Dependent Strength
• Full Numerical Simulations of Catastrophic Small Body Collisions
• Kuiper Belt-Like Hot and Cold Populations of Planetesimal Inclinations in the $\beta$ Pictoris Belt Revealed by ALMA
• Investigating the young AU~Mic system with SPIRou: large-scale stellar magnetic field and close-in planet mass
• Planet-induced radio emission from the coronae of M dwarfs: the case of Prox Cen and AU Mic
• The AU Microscopii Debris Disk: Multiwavelength Imaging and Modeling
• ALMA observations of the debris disk around the young Solar Analog HD 107146
• Planet populations inferred from debris discs: insights from 178 debris systems in the ISPY, LEECH and LIStEN planet-hunting surveys
• The Mass of Stirring Bodies in the AU Mic Debris Disk Inferred from Resolved Vertical Structure
• Debris Disc Constraints on Planetesimal Formation
• Simulating the Space Weather in the AU Mic System: Stellar Winds and Extreme Coronal Mass Ejections
• The vertical structure of debris disks and the impact of gas
• Expelled grains from an unseen parent body around AU Mic
• Stellar Winds and Dust Avalanches in the AU Mic Debris Disk
• Rave: A non-parametric method for recovering the surface brightness and height profiles of edge-on debris disks
• The far reaches of the beta Pictoris debris disk
• ALMA and VLA Observations of the HD 141569 System
• Relating grain size distributions in circumstellar discs to the spectral index at millimetre wavelengths
• Near-Infrared Image of the Debris Disk around HD 15115
• Four new PLanetesimals Around TYpical and Pre-main seqUence Stars (PLATYPUS) Debris Discs at 8.8mm
• Multi-wavelength, spatially resolved modelling of HD 48682's debris disc

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