Requirements for gravitational collapse in planetesimal formation

• Verfasst von: Gerbig, Konstantin [VerfasserIn]
• Verfasst von: Murray-Clay, Ruth A. [VerfasserIn]
• Verfasst von: Klahr, Hubertus [VerfasserIn]
• Verfasst von: Baehr, Hans-Paul Frederick [VerfasserIn]
• Titel: Requirements for gravitational collapse in planetesimal formation
• Titelzusatz: the impact of scales set by Kelvin-Helmholtz and nonlinear streaming instability
• Verf.angabe: Konstantin Gerbig, Ruth A. Murray-Clay, Hubert Klahr, and Hans Baehr
• E-Jahr: 2020
• Jahr: 2020 June 1
• Umfang: 20 S.
• Fussnoten: Gesehen am 06.10.2022
• Titel Quelle: Enthalten in: The astrophysical journal / 1
• Ort Quelle: London : Institute of Physics Publ., 1995
• Jahr Quelle: 2020
• Band/Heft Quelle: 895(2020), 2, Artikel-ID 91, Seite 1-20
• ISSN Quelle: 1538-4357
• DOI: doi:10.3847/1538-4357/ab8d37
• Datenträger: Online-Ressource
• Sprache: eng
• K10plus-PPN: 1818118890

Abstract

The formation of planetesimals is a challenging problem in planet formation theory. A prominent scenario for overcoming dust growth barriers is the gravitational collapse of locally over-dense regions, shown to robustly produce ∼100 km-sized objects. Still, the conditions under which planetesimal formation occurs remain unclear. For collapse to proceed, the self-gravity of an over-density must overcome stellar tidal disruption on large scales and turbulent diffusion on small scales. Here, we relate the scales of streaming and Kelvin-Helmholtz instability (KHI), which both regulate particle densities on the scales of gravitational collapse, directly to planetesimal formation. We support our analytic findings by performing 3D hydrodynamical simulations of streaming and KHI and planetesimal formation. We find that the vertical extent of the particle mid-plane layer and the radial width of streaming instability filaments are set by the same characteristic length scale, thus governing the strength of turbulent diffusion on the scales of planetesimal formation. We present and successfully test a collapse criterion, 0.1Q β ϵ−1Z−1 ≲ 1, and show that even for solar metallicities, planetesimals can form in dead zones of sufficiently massive disks. For a given gas Toomre parameter Q, pressure gradient β, metallicity Z, and local particle enhancement ϵ, the collapse criterion also provides a range of unstable scales, instituting a promising path for studying initial planetesimal mass distributions. Streaming instability is not required for planetesimal collapse but, by increasing ϵ, can evolve a system to instability.