Relating grain size distributions in circumstellar discs to the spectral index at millimetre wavelengths

Abstract

The excess emission seen in spectral energy distributions (SEDs) is commonly used to infer the properties of the emitting circumstellar dust in protoplanetary and debris discs. Most notably, dust size distributions and details of the collision physics are derived from SED slopes at long wavelengths. This paper reviews the approximations that are commonly used and contrasts them with numerical results for the thermal emission. The inferred size distribution indexes are shown to be greater and more sensitive to the observed sub(mm) spectral indexes than previously considered. This effect results from aspects of the transition from small grains with volumetric absorption to bigger grains that absorb and emit near to their surface, controlled by both the real and the imaginary part of the refractive index. The steeper size distributions indicate stronger size-dependence of material strengths or impact velocities or, otherwise, less efficient transport or erosion processes. Strong uncertainties remain because of insufficient knowledge of the material composition, porosity, and optical properties at long wavelengths.

accepted for publication in Astronomy & Astrophysics, 13 pages, 14 figures

References in corpus (19)

• The Gaia mission
• Steady-State Size Distributions for Collisional Populations: Analytical Solution with Size-Dependent Strength
• Collisional processes and size distribution in spatially extended debris discs
• Disk Radii and Grain Sizes in Herschel-Resolved Debris Disks
• Outer edges of debris discs: how sharp is sharp?
• A Complete ALMA Map of the Fomalhaut Debris Disk
• Survival of icy grains in debris discs. The role of photosputtering
• ALMA observations of the $\eta$ Corvi debris disc: inward scattering of CO-rich exocomets by a chain of 3-30 M${}_{\oplus }$ planets?
• Kuiper Belt-Like Hot and Cold Populations of Planetesimal Inclinations in the $\beta$ Pictoris Belt Revealed by ALMA
• Collisional and Thermal Emission Models of Debris Disks: Towards Planetesimal Population Properties
• The Northern Arc of $\epsilon$ Eridani's Debris Ring as Seen by ALMA
• ALMA observations of the narrow HR 4796A debris ring
• ALMA Detection of Extended Millimeter Halos in the HD 32297 and HD 61005 Debris Disks
• Debris Disc Constraints on Planetesimal Formation
• Multiple Rings of Millimeter Dust Emission in the HD 15115 Debris Disk
• ALMA 1.3 Millimeter Map of the HD 95086 System
• Discovery of Resolved Debris Disk Around HD 131835
• The influence of dust grain porosity on the analysis of debris disc observations
• Absorption of crystalline water ice in the far infrared at different temperatures

Cited by in corpus (8)

• Constraining planetesimal stirring: how sharp are debris disc edges?
• Multiwavelength Vertical Structure in the AU Mic Debris Disk: Characterizing the Collisional Cascade
• The ALMA survey to Resolve exoKuiper belt Substructures (ARKS) II. The radial structure of debris discs
• Atacama Large Aperture Submillimeter Telescope (AtLAST) Science: Our Galaxy
• Hiding Dust Around $\epsilon$ Eridani
• Four new PLanetesimals Around TYpical and Pre-main seqUence Stars (PLATYPUS) Debris Discs at 8.8mm
• The Disks In Scorpius-Centaurus Survey (DISCS) I: Four Newly-Resolved Debris Disks in Polarized Intensity Light
• The impact of the presence of water ice on the analysis of debris disk observations