Dust production in debris discs: constraints on the smallest grains

Abstract

The surface energy constraint puts a limit on the smallest fragment $s_{surf}$ that can be produced after a collision. Based on analytical considerations, this mechanism has been recently identified as been potentially able to prevent the production of small dust grains in debris discs and cut off their size distribution at sizes larger than the blow-out size. We numerically investigate the importance of this effect to find under which conditions it can leave a signature in the small-size end of a disc's particle size distribution (PSD). An important part of this work is to map out, in a disc at steady-state, what is the most likely collisional origin for micron-sized grains, in terms of the sizes of their collisional progenitors. We implement, for the first time, the surface energy constraint into a collisional evolution code. We consider a debris disc extending from 50 to 100AU and 2 different stellar types. We also consider two levels of stirring in the disc: dynamically "hot" (e=0.075) and "cold" (e=0.01). For all cases, we derive $s_{surf}$ maps as a function of target and projectile sizes, $s_t$ and $s_p$, and compare them to equivalent maps for the dust-production rate. We then compute disc-integrated PSDs and estimate the imprint of the surface energy constraint. We find that the ($s_p$,$s_t$) regions of high $s_{surf}$ values do not coincide with those of high dust production rate. As a consequence, the surface energy constraint has generally a weak effect on the system's PSD. The maximum $s_{surf}$-induced depletion of $\mu$m-sized grains is $\sim 30$% and is obtained for a sun-like star and a dynamically hot case. For the e=0.01 cases, the surface energy effect is negligible compared to the massive small grain depletion induced by another mechanism: the natural imbalance between dust production and destruction rates in low-stirring discs identified by Thebault&Wu(2008).

Accepted for Publication in A&A (abstract truncated for astroph) (v3 and v4 corrected from minor language errors and typos)

References in corpus (8)

• Long-Term Collisional Evolution of Debris Disks
• 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?
• Collisional dust avalanches in debris discs
• A Ring of Warm Dust in the HD 32297 Debris Disk
• A dearth of small particles in debris disks: An energy-constrained smallest fragment size
• Collisional modelling of the debris disc around HIP 17439

Cited by in corpus (11)

• How to design a planetary system for different scattering outcomes: giant impact sweet spot, maximising exocomets, scattered disks
• A $75\%$ Occurrence Rate of Debris Discs around F stars in the $\beta$ Pic Moving Group
• The Inner 25 AU Debris Distribution in the epsilon Eri System
• Is there more than meets the eye? Presence and role of submicron grains in debris discs
• Transient events in bright debris discs: Collisional avalanches revisited
• The influence of dust grain porosity on the analysis of debris disc observations
• The beta Pictoris system: Setting constraints on the planet and the disk structures at mid-IR wavelengths with NEAR
• A multi-wavelength study of the debris disc around 49 Cet
• Characterization of debris disks observed with SPHERE
• 94 Ceti: a triple star with a planet and dust disc
• The impact of the presence of water ice on the analysis of debris disk observations