Can dust coagulation trigger streaming instability?

Abstract

Context. Streaming instability can be a very efficient way of overcoming growth and drift barriers to planetesimal formation. However, it was shown that strong clumping, which leads to planetesimal formation, requires a considerable number of large grains. State-ofthe-art streaming instability models do not take into account realistic size distributions resulting from the collisional evolution of dust. Aims. We investigate whether a sufficient quantity of large aggregates can be produced by sticking and what the interplay of dust coagulation and planetesimal formation is. Methods. We develop a semi-analytical prescription of planetesimal formation by streaming instability and implement it in our dust coagulation code based on the Monte Carlo algorithm with the representative particles approach. Results. We find that planetesimal formation by streaming instability may preferentially work outside the snow line, where sticky icy aggregates are present. The efficiency of the process depends strongly on local dust abundance and radial pressure gradient, and requires a super-solar metallicity. If planetesimal formation is possible, the dust coagulation and settling typically need ∼100 orbits to produce sufficiently large and settled grains and planetesimal formation lasts another ∼1000 orbits. We present a simple analytical model that computes the amount of dust that can be turned into planetesimals given the parameters of the disk model.

X-ray photoevaporation’s limited success in the formation of planetesimals by the streaming instability

“…Drażkowska & Dullemond (2014) show that Z crit strongly depends on particle size, or more precisely on the dimensionless stopping time (Stokes number, St). For metallicities 10 −2 , Drażkowska & Dullemond (2014) show that Stokes numbers of order 10 −2 are sufficient to trigger the instability, and Carrera et al (2015) extend the condition down to Stokes numbers of order 10 −3 for similar Z.…”

“…Drażkowska & Dullemond (2014) show that Z crit strongly depends on particle size, or more precisely on the dimensionless stopping time (Stokes number, St). For metallicities 10 −2 , Drażkowska & Dullemond (2014) show that Stokes numbers of order 10 −2 are sufficient to trigger the instability, and Carrera et al (2015) extend the condition down to Stokes numbers of order 10 −3 for similar Z. The exact critical values for Z and St are subject to further complications; simulations show that for larger pressure gradients (higher drift speeds), the metallicity threshold for clumping increases (Bai & Stone 2010), and this effect is not taken into account in the estimates above.…”

Linear growth of streaming instability in pressure bumps

“…The robustness of the streaming instability has been tested against several numerical schemes (Balsara et al 2009;Miniati 2010;Tilley et al 2010;Bai & Stone 2010a;Johansen et al 2012Johansen et al , 2014, towards the aim of simulating its E-mail: mailto:guillaume.laibe@ens-lyon.fr effect in a global disc (Lyra & Kuchner 2013;Kowalik et al 2013;Yang & Johansen 2014). Other physical processes such as vortices (Raettig et al 2015), photo-evaporation (Carrera et al 2017), presence of small grains (Laibe & Price 2014), grain growth (Drażkowska & Dullemond 2014) or snow lines (Schoonenberg & Ormel 2017) may reinforce the ability of streaming instability to concentrate dust.…”

Comet formation in collapsing pebble clouds

“…The SI avoids the growth barriers by jumping directly from pebbles with Stokes number St ∼ 0.01−1 (corresponding to a grain size of mm to dm, depending on the radial location in the disk) to Ceres-sized planetesimals (Johansen et al 2007;Bai & Stone 2010;Drażkowska & Dullemond 2014). The SI is triggered once the local dust-to-gas ratio in the protoplanetary disk exceeds unity.…”