The influence of dust grain porosity on the analysis of debris disc observations
AffiliationUniv Arizona, Dept Astron, Steward Observ
MetadataShow full item record
PublisherOXFORD UNIV PRESS
CitationThe influence of dust grain porosity on the analysis of debris disc observations 2017, 464 (4):4383 Monthly Notices of the Royal Astronomical Society
Rights© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
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AbstractDebris discs are often modelled assuming compact dust grains, but more and more evidence for the presence of porous grains is found. We aim at quantifying the systematic errors introduced when modelling debris discs composed of porous dust with a disc model assuming spherical, compact grains. We calculate the optical dust properties derived via the fast, but simple effective medium theory. The theoretical lower boundary of the size distribution - the so-called 'blowout size' - is compared in the cases of compact and porous grains. Finally, we simulate observations of hypothetical debris discs with different porosities and feed them into a fitting procedure using only compact grains. The deviations of the results for compact grains from the original model based on porous grains are analysed. We find that the blowout size increases with increasing grain porosity up to a factor of 2. An analytical approximation function for the blowout size as a function of porosity and stellar luminosity is derived. The analysis of the geometrical disc set-up, when constrained by radial profiles, is barely affected by the porosity. However, the determined minimum grain size and the slope of the grain size distribution derived using compact grains are significantly overestimated. Thus, the unexpectedly high ratio of minimum grain size to blowout size found by previous studies using compact grains can be partially described by dust grain porosity, although the effect is not strong enough to completely explain the trend.
VersionFinal published version
SponsorsDFG [WO 857/13-1, WO 857/15-1]