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Title: Streaming Instability and Turbulence: Conditions for Planetesimal Formation
Abstract The streaming instability (SI) is a leading candidate for planetesimal formation, which can concentrate solids through two-way aerodynamic interactions with the gas. The resulting concentrations can become sufficiently dense to collapse under particle self-gravity, forming planetesimals. Previous studies have carried out large parameter surveys to establish the critical particle to gas surface density ratio (Z), above which SI-induced concentration triggers planetesimal formation. The thresholdZdepends on the dimensionless stopping time (τs, a proxy for dust size). However, these studies neglected both particle self-gravity and external turbulence. Here, we perform 3D stratified shearing box simulations with both particle self-gravity and turbulent forcing, which we characterize via a turbulent diffusion parameter,αD. We find that forced turbulence, at amplitudes plausibly present in some protoplanetary disks, can increase the thresholdZby up to an order of magnitude. For example, forτs= 0.01, planetesimal formation occurs whenZ≳ 0.06, ≳0.1, and ≳0.2 atαD= 10−4, 10−3.5, and 10−3, respectively. We provide a single fit to the criticalZrequired for the SI to work as a function ofαDandτs(although limited to the rangeτs= 0.01–0.1). Our simulations also show that planetesimal formation requires a mid-plane particle-to-gas density ratio that exceeds unity, with the critical value being largely insensitive toαD. Finally, we provide an estimation of particle scale height that accounts for both particle feedback and external turbulence.  more » « less
Award ID(s):
2007422
PAR ID:
10621845
Author(s) / Creator(s):
; ; ; ; ; ; ; ;
Publisher / Repository:
American Astronomical Society
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
969
Issue:
2
ISSN:
0004-637X
Page Range / eLocation ID:
130
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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