Does warm debris dust stem from asteroid belts?

Abstract

Many debris discs reveal a two-component structure, with a cold outer and a warm inner component. While the former are likely massive analogues of the Kuiper belt, the origin of the latter is still a matter of debate. In this work we investigate whether the warm dust may be a signature of asteroid belt analogues. In the scenario tested here the current two-belt architecture stems from an originally extended protoplanetary disc, in which planets have opened a gap separating it into the outer and inner discs which, after the gas dispersal, experience a steady-state collisional decay. This idea is explored with an analytic collisional evolution model for a sample of 225 debris discs from a Spitzer/IRS catalogue that are likely to possess a two-component structure. We find that the vast majority of systems (220 out of 225, or 98%) are compatible with this scenario. For their progenitors, original protoplanetary discs, we find an average surface density slope of $-0.93\pm 0.06$ and an average initial mass of $\left(3.3_{-0.3}^{+0.4}\right)\times 10^{-3}$ solar masses, both of which are in agreement with the values inferred from submillimetre surveys. However, dust production by short-period comets and - more rarely - inward transport from the outer belts may be viable, and not mutually excluding, alternatives to the asteroid belt scenario. The remaining five discs (2% of the sample: HIP 11486, HIP 23497, HIP 57971, HIP 85790, HIP 89770) harbour inner components that appear inconsistent with dust production in an "asteroid belt." Warm dust in these systems must either be replenished from cometary sources or represent an aftermath of a recent rare event, such as a major collision or planetary system instability.

Accepted for publication in MNRAS, 12 pages and 12 figures

References in corpus (15)

• Transience of hot dust around sun-like stars
• Variations on Debris Disks: Icy Planet Formation at 30-150 AU for 1-3 Solar Mass Main Sequence Stars
• Long-Term Collisional Evolution of Debris Disks
• Steady-State Size Distributions for Collisional Populations: Analytical Solution with Size-Dependent Strength
• Resolved Debris Discs Around A Stars in the Herschel DEBRIS Survey
• Do Two Temperature Debris Disks Have Multiple Belts?
• The History of the Solar System's Debris Disc: Observable Properties of the Kuiper Belt
• Disk Radii and Grain Sizes in Herschel-Resolved Debris Disks
• A near-infrared interferometric survey of debris-disc stars. IV. An unbiased sample of 92 southern stars observed in H-band with VLTI/PIONIER
• ALMA observations of the debris disk around the young Solar Analog HD 107146
• Mid-infrared resolution of a 3 AU-radius debris disk around Zeta Leporis
• Inner mean-motion resonances with eccentric planets: A possible origin for exozodiacal dust clouds
• Warm exo-Zodi from cool exo-Kuiper belts: the significance of P-R drag and the inference of intervening planets
• The discovery of new warm debris disks around F-type stars
• Collisional modelling of the debris disc around HIP 17439